Features new to Windows XP

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As the next version of Windows NT after Windows 2000, as well as the successor to Windows Me, Windows XP introduced many new features but it also removed some others.

With the introduction of Windows XP, the C++ based software-only GDI+ subsystem was introduced to replace certain GDI functions. GDI+ adds anti-aliased 2D graphics, textures, floating point coordinates, gradient shading, more complex path management, bicubic filtering, intrinsic support for modern graphics-file formats like JPEG and PNG, and support for composition of affine transformations in the 2D view pipeline. GDI+ uses RGBA values to represent color. Use of these features is apparent in Windows XP's user interface (transparent desktop icon labels, drop shadows for icon labels on the desktop, shadows under menus, translucent blue selection rectangle in Windows Explorer, sliding task panes and taskbar buttons), and several of its applications such as Microsoft Paint, Windows Picture and Fax Viewer, Photo Printing Wizard, My Pictures Slideshow screensaver, and their presence in the basic graphics layer greatly simplifies implementations of vector-graphics systems such as Flash or SVG. The GDI+ dynamic library can be shipped with an application and used under older versions of Windows. The total number of GDI handles per session is also raised in Windows XP from 16,384 to 65,536 (configurable through the registry).

Windows XP shipped with DirectX 8.1, which brings major new features to DirectX Graphics besides DirectX Audio (both DirectSound and DirectMusic), DirectPlay, DirectInput and DirectShow. Direct3D introduced programmability in the form of vertex and pixel shaders, enabling developers to write code without worrying about superfluous hardware state, and fog, bump mapping and texture mapping. DirectX 9 was released in 2003, which also sees major revisions to Direct3D, DirectSound, DirectMusic and DirectShow.^[1] Direct3D 9 added a new version of the High-Level Shader Language,^[2] support for floating-point texture formats, Multiple Render Targets, and texture lookups in the vertex shader. Windows XP can be upgraded to DirectX 9.0c (Shader Model 3.0).

Windows XP includes ClearType subpixel rendering, which makes onscreen fonts smoother and more readable on liquid-crystal display (LCD) screens.^[3][4] Although ClearType has an effect on CRT monitors, its primary use is for LCD/TFT-based (laptop, notebook and modern 'flatscreen') displays. ClearType in Windows XP currently supports the RGB and BGR sub pixel structures. There are other parameters such as contrast that can be set via a ClearType Tuner powertoy that Microsoft makes available as a free download from its Typography website.^[5]

With Windows XP, the Start button has an updated appearance and is larger, making it faster to mouse over to it and click it. To help the user access a wider range of common destinations more easily from a single location, the Start menu was expanded to two columns; the left column focuses on the user's installed applications, while the right column provides access to the user's documents, and system links which were previously located on the desktop. Links to the My Documents, My Pictures and other special folders are brought to the fore. The My Computer and My Network Places (Network Neighborhood in Windows 95 and 98) icons were also moved off the Desktop and into the Start menu, making it easier to access these icons while a number of applications are open and so that the desktop remains clean. Moreover, these links can be configured to expand as a cascading menu. Frequently used programs are automatically displayed in the left column, newly installed programs are highlighted, and the user may opt to "pin" programs to the start menu so that they are always accessible without having to navigate through the Programs folders. The default web browser and default email program are pinned to the Start menu. The Start menu is fully customizable, links can be added or removed; the number of frequently used programs to display can be set. The All Programs menu expands like the classic Start menu to utilize the entire screen but can be set to scroll programs. The user's name and user's account picture are also shown on the Start menu.

The taskbar buttons for running applications and Quick Launch have also been updated for Fitt's law. Locking the taskbar not only prevents it from being accidentally resized or moved but elements such as Quick launch and other DeskBands are also locked from being accidentally moved. The Taskbar grouping feature combines multiple buttons of the same application into a single button, which when clicked, pops up a menu listing all the grouped windows and their number. Advanced taskbar grouping options can be configured from the registry.^[6] The user can choose to always show, always hide or hide some or all notification area icons if inactive for some time. A button allows the user to reveal all the icons. The Taskbar, if set to a thicker height also displays the day and date in the notification area.

There are significant changes made to Windows Explorer in Windows XP, both visually and functionally. Microsoft focused especially on making Windows Explorer more discoverable and task-based, as well as adding a number of features to reflect the growing use of a computer as a "digital hub".

The task pane is displayed on the left side of the window instead of the traditional folder tree view when the navigation pane is turned off. It presents the user with a list of common actions and destinations that are relevant to the current directory or file(s) selected. For instance, when in a directory containing mostly pictures, a set of "Picture tasks" is shown, offering the options to display these pictures as a slide show, to print them, or to go online to order prints. Conversely, a folder containing music files would offer options to play those files in a media player, or to go online to purchase music.

Every folder also has "File and Folder Tasks", offering options to create new folders, share a folder on the local network, publish files or folders to a web site using the Web Publishing Wizard, and other common tasks like copying, renaming, moving, and deleting files or folders. File types that have identified themselves as being printable also have an option listed to print the file.

Underneath "File and Folder Tasks" is "Other Places", which always lists the parent folder of the folder being viewed and includes additional links to other common locations such as "My Computer", "Control Panel", and "My Documents" or previously navigated locations. These change depending on what folder the user was in.

Underneath "Other Places" is a "Details" area which gives additional information when a file or folder is selected – typically the file type, file size and date modified, but depending on the file type, author, image dimensions, attributes, or other details. If the file type has a Thumbnail image handler installed, its preview also appears in the "Details" task pane. For music files, it might show the artist, album title, and the length of the song. The same information is also shown horizontally on the status bar.

The "Folders" button on the Windows Explorer toolbar toggles between the traditional navigation pane containing the tree view of folders, and the task pane. Users can also close the navigation pane by clicking the Close button in its right corner as well as turn off the task pane from Folder Options.

The navigation pane has been enhanced in Windows XP to support "simple folder view" which when turned on hides the dotted lines that connect folders and subfolders and makes folders browsable with single click while still keeping double clicking on in the right pane. Single clicking in simple folder view auto expands the folder and clicking another folder automatically expands that folder and collapses the previous one.

Windows XP introduced a large number of metadata properties^[7] which are shown as columns in the "Details" view of Explorer, in the new Tiles view in Explorer, on the Summary tab in a file's properties, in a file's tooltip and on the Explorer status bar when a single file is selected. Users also gain the ability to sort by any property which is turned on in "Details" view. Developers can write column handler shell extensions to further define their own properties by which files can be sorted. The column by which items are sorted is highlighted. Sorting files and folders can be in Ascending order or Descending order in all views, not just Details view. To reverse the order, the user simply can perform the sort by the same property again. The sort order has also been made more intuitive compared to the one in Windows 2000. For file names containing numbers Windows Explorer now tries to sort based on numerical value rather than just comparing each number digit by digit for every character position in the file name.^[8] For instance, files containing "1", "2".."10" will be intuitively sorted with "10" appearing after "9" instead of appearing between "1" and "2".

The right pane of Windows Explorer has a "Show in Groups" feature which allows Explorer to separate its contents by headings based on any field which is used to sort the items. Items can thus be grouped by any detail which is turned on. "Show in Groups" is available in Thumbnails, Tiles, Icons and Details views.

Microsoft introduced animated "Search Companions" in an attempt to make searching more engaging and friendly; the default character is a puppy named Rover, with three other characters (Merlin the magician, Earl the surfer, and Courtney) also available. These search companions powered by Microsoft Agent technology, bear a great deal of similarity to Microsoft Office's Office Assistants, even incorporating "tricks" and sound effects. If the user wishes, they can also turn off the animated character entirely.

The search capability itself is fairly similar to Windows Me and Windows 2000, with some important additions. The Indexing Service can extract Exif properties, as well as some metadata for ASF, WMV and MP3 files under Windows XP via the IPropertyStorage interface using built-in Null Filter. Search can also be instructed to search only files that are categorically "Documents" or "Pictures, music and video" (searching by perceived type); this feature is noteworthy largely because of how Windows determines what types of files can be classified under these categories.^[9] Another important addition is that the "Look in" field accepts and expands environment variables for abbreviated entry of long paths. Also, users can configure whether or not Windows XP searches for system and/or hidden files and folders. Using Tweak UI, the search user interface can be restored to the one used by Windows 2000.

Windows XP improves image preview by offering a Filmstrip view which shows images in a single horizontal row and a large preview of the currently selected image above it. "Back" and "Previous" buttons facilitate navigation through the pictures, and a pair of "Rotate" buttons offer 90-degree clockwise and counter-clockwise rotation of images. Filmstrip view like any other view can be turned on per folder. This view will be available if the new "Common Tasks" folder view is selected, not with "Windows Classic" folder view. Aside from the Filmstrip view mode, there is a 'Thumbnails' view, which displays thumbnail-sized images in the folder and also displays images a subfolder may be containing (4 by default) overlaid on a large folder icon. A folder's thumbnail view can be customized from the Customize tab accessible from its Properties, where users can also change the folder's icon and specify a template type (pictures, music, videos, documents) for that folder and optionally all its subfolders. The size and quality of thumbnails in "Thumbnails" view can be adjusted using Tweak UI or the registry.^[10] Exif metadata stored in the image is also shown in the file's Properties -> Summary tab, in "Details" view and in any view on the status bar. Windows XP optionally caches the thumbnails in a "Thumbs.db" file in the same folder as the pictures so that thumbnails are generated faster the next time. Thumbnails can be forced to regenerate by right-clicking the image in Thumbnail or Filmstrip views and selecting "Refresh thumbnail".

AutoPlay examines newly discovered removable media and devices and, based on content such as pictures, music or video files, launches an appropriate application to play or display the content.^[11] AutoPlay (not to be confused with AutoRun) was created in order to simplify the use of peripheral devices – MP3 players, memory cards, USB storage devices and others – by automatically starting the software needed to access and view the content on these devices. AutoPlay can be enhanced by AutoPlay-compatible software and hardware. It can be configured by the user to associate favourite applications with AutoPlay events and actions. These actions are called AutoPlay Handlers and there are sets of Handlers associated with various types of content. New AutoPlay handlers can get added to the system when additional software is installed. The user can edit, delete or create AutoPlay handlers using TweakUI. AutoPlay settings can be configured per-device in Windows XP from the device's properties.

When a user inserts an optical disc into a drive or attaches a USB camera, Windows detects the arrival and starts a process of examining the device or searching the medium. It is looking for properties of the device or content on the medium so that AutoPlay can present a set of meaningful options to the user. When the user makes a particular choice, they also have the option to make that selection automatic the next time Windows sees that content or device.^[12] The content types available vary with the type of drive selected.

• Windows XP introduced the notion of Perceived Types, making it easier for applications and shell extensions to register themselves with file types, even if the default program and its associated ProgID changes.^[13] Perceived Types also made it easier for end users to search files without specifying individual file extensions.
• Per-user Recycle Bin for NTFS volumes. In earlier versions of Windows NT, one user could see the other user's deleted files located in the Recycle Bin.
• Folder options to restore previously open folder windows at logon (restoring Explorer sessions)^[14]
• Customizable infotips on a per-file-class (file type) basis without writing shell extensions^[15]
• Windows Explorer is content-dependent, that is, it attempts to detect the dominant type of files in a folder and then selects the most appropriate view for the user automatically unless the user manually sets the view.
• To prevent applications from taking over the file associations already registered with the default program explicitly set by the user, Windows XP prevents programmatic file associations if the Open With dialog or File Types tab is used by users to override the default.
• A "Tiles" view was added, which displays the file's icon in a larger size (48 × 48), and places the file name, descriptive type, and additional information by which the items are sorted (typically the file size for data files, and the publisher name for applications) to the right.
• The toolbars can be locked to prevent them from being accidentally moved. This same capability was also added to Internet Explorer's toolbars.
• The "Line up icons" feature in the context menu has been replaced by an "Align to grid" feature which when turned on always lines up icons.
• For unknown/undefined file types which inexperienced users may get confused when double clicked, Windows XP can contact a web service which shows additional information about that file type and what program created or can open that file type.
• If an image named "Folder.jpg" is placed inside a folder, that image will be used as the thumbnail for that folder and as Album Art for media files in Windows Media Player.
• EFS-encrypted files can be shown in an alternate color (green by default) beginning with Windows XP.
• File and folder size information is shown in tooltips upon mouse hover. For folders, size and partial folder contents are shown.
• When opening more than 15 files in a single operation, i.e. by selecting multiple files and pressing enter, Windows XP warns the user that Windows Explorer may become unresponsive, but still allows the user to do so.
• Windows Explorer supports a very basic form of mass renaming items.
• Marquee-style progress bars.
• A hyperlink control in system supplied common controls.

Windows XP includes Windows Picture and Fax Viewer which is based on GDI+^[16] and is capable of viewing image formats supported by GDI+, namely, JPEG, BMP, PNG, GIF (including animated GIFs), ICO, WMF, EMF and TIFF format files. It supersedes part of the functions of Imaging for Windows in previous versions of Windows.

The Windows Picture and Fax Viewer is integrated with Windows Explorer for functions like slideshow, email, printing etc. and quickly starts up when an image is double clicked in Windows Explorer. It supports full file management from within the viewer itself, that is, right clicking the image shows the same context menu as the one shown when an image is right clicked in Windows Explorer. Images can be set as the desktop wallpaper from the context menu. It supports successive viewing of all images in current folder and looping through images,^[17] that is, after viewing the last image in a directory, it again shows the first image and vice versa. By default, images smaller than the user's display resolution are shown at their actual size. If an image is larger than the display resolution, it is scaled to fit the screen (Best Fit).^[17] Images can be zoomed in or out depending on the viewing area. When this is done, scroll bars allow for viewing of all areas of the image. It has Standard toolbar buttons for Delete, Print, Copy to and Open with.^[17] The Copy to button converts an image to a different format supported in GDI+, that is, JPEG, BMP, GIF, TIFF or PNG.^[18] The Print button starts the Photo Printing Wizard which allows printing images with picture titles using various page layouts such as full page prints, wallet prints, contact/index sheets or certain fixed dimensions with the images cropped or rotated to fit the page. The wizard shows a preview of what the printed page will look like with the currently specified options.^[18] Windows Picture and Fax Viewer can also rotate images clockwise or anti-clockwise, start a slideshow of all or selected images in the folder, or e-mail them by selecting the "Send To Mail Recipient" option.^[18] Further options allow the image to be mailed full size, or in pixel dimensions of: 640 x 480, 800 x 600, and 1024 x 768. Using Tweak UI, the time between images during a slideshow can be adjusted.

Windows Picture and Fax Viewer recognizes embedded ICC V2 color profiles^[19] in JPG and TIFF files. GIF files are shown with full animation, even when zoomed. TIFF files can be annotated using the Annotation Toolbar which appears at the bottom of the screen.^[20] Lines can be drawn on the TIFF image and text added to it. Areas of the image can be selected and concealed. The Windows Picture and Fax Viewer is also capable of viewing multi-page TIFF files. However TIFF images with JPEG compression are not fully supported.^[21] The last button on the standard toolbar opens the image for editing; by default, in Microsoft Paint; however any editing application can be registered for this button in the viewer. Windows Picture and Fax Viewer saves and remembers its window position and size and supports keyboard shortcuts for all of its operations.

Raw image formats, which are the preferred formats in professional photography are not supported, however, Microsoft released a later update called RAW Image Thumbnailer and Viewer for Windows XP for viewing certain raw image files.^[22]

• Windows XP includes a new set of visual styles, known by its codename, "Luna". Available in three color schemes, the interface is more task-based than the basic one included since Windows 95, with options available in Explorer windows to interact with each file. The user can however choose to fully revert to the pre-Windows XP "classic" user interface. Developers can take advantage of visual styles through the use of Comctl32.dll v6.0 in their programs.^[23]
• Windows XP's Display Properties allows users to save their customizations as Themes. This feature was previously a part of Microsoft Plus!.
• Icon and cursor support for 24-bit color depth with an 8-bit alpha channel.^[24] Microsoft contracted The Iconfactory which created over 100 colorful icons for Microsoft to be included in Windows XP.^[25] The 10-icon resource limit has also been increased.^[26] For high DPI displays, Windows XP supports larger cursor sizes.^[27]
• Use of bullets instead of asterisks in password fields of a TextBox control, i.e., "•••" instead of "***".
• Several informational, critical and warning messages in Windows XP are shown as balloon notifications which automatically fade away after predefined interval and condition, instead of showing them as dialog boxes which require interaction from the user.
• New configurable sound events for Device Connect, Device Disconnect, Device Failed to Connect, Print Complete, New fax, Fax Error, System Notification, Windows Logon and Windows Logoff.
• A set of live orchestral recordings for the Windows XP tour theme music and system sounds was composed by composer Bill Brown.^[28]
• The music that plays during the Out-of-box experience, the setup at first launch where the user could connect to the internet, choose whether to have automatic updates, and choose their username, is located at C:\Windows\system32\oobe\images\title.wma. The piece is named "Windows Welcome music" or "Velkommen" and was composed by Stan LePard. This piece was also used in the tour for Internet Explorer 3 Starter Kit.^[29][30][31]
• Window ghosting that allows the user to minimize, move or close the main window even if the application is not responding.^[32]

The Text Services Framework (TSF), is a COM framework and API introduced in Windows XP that supports advanced text input and text processing. The Text Services Framework is designed to offer advanced language and word processing features to applications. It supports features such as multilingual support, keyboard drivers, handwriting recognition, speech recognition, as well as spell checking and other text and natural language processing functions. It is also downloadable for older Windows operating systems.^[33]

The Language Bar is the core user interface for Text Services Framework. The language bar enables text services to add UI elements to the toolbar and enables these elements when an application has focus. From the Language Bar, users can select the input language, and control keyboard input, handwriting recognition and speech recognition. The language bar also provides a direct means to switch between installed languages, even when a non-TSF-enabled application has focus.

The Windows XP kernel is completely different from the kernel of the Windows 9x/Me line of operating systems. Although an upgrade of the Windows 2000 kernel, there are major scalability, stability and performance improvements, albeit transparent to the end user.^[34][35]

Windows XP includes simultaneous multithreading (hyperthreading) support. Simultaneous multithreading is a processor's ability to process more than one data thread per core at a time.

Windows XP supports a larger system virtual address space—1.3 GB—of which the contiguous virtual address space that can be used by device drivers is 960 MB. The Windows XP Memory Manager is redesigned to consume less paged pool, allowing for more caching and greater availability of paged pool for any component that needs it.

The total size of memory-mapped files in Windows 2000 was limited because the memory manager allocated the Prototype Page Table entries (PPTEs) for the entire file, even if an application created mapped views to only parts of the file. In Windows XP, the Prototype PTEs are only allocated when required by an application, allowing larger mapped files. A benefit of this, for example, is in case of making backups of large files on low memory systems. The paged pool limit of 470 MB has been lifted from the Memory Manager in Windows XP, with unmapped views dynamically reusable by the memory manager depending on pool usage.

Memory pages in working sets are trimmed more efficiently for multiprocessor systems depending on how recently they were accessed. Lock contention is reduced, as a number of unnecessary locks used in resource synchronizations (RAM allocation and mapping through Address Windowing Extensions, system page table entries, charging non-paged/paged pool quotas, charging commitment of pages) have been removed. The dispatcher lock contention has been reduced and the Page Frame Number (PFN) lock has been optimized for increased parallelism and granularity. Windows XP uses push locks on the event synchronization object if there is no contention as they support shared and exclusive acquisition. Push locks protect handle table entries in the Executive, and in the Object Manager (to protect data structures and security descriptors) and Memory Manager (to protect AWE-related locks). Windows XP uses the SYSENTER/SYSEXIT mechanisms which require fewer clock cycles to transition to and from user mode to kernel mode to speed up system calls.

The kernel page write protection limit in Windows XP is enabled on systems up to 256 MB of RAM beyond which large pages are enabled for increased address translation performance.

Windows XP introduces the CreateMemoryResourceNotification function which can notify user mode processes of high or low memory availability so applications can allocate more memory or free up memory as necessary.^[36]

In versions of Windows prior to Windows XP, the registry size was limited to 80% of the paged pool size. In Windows XP, the registry is reimplemented outside of the paged pool; the registry hives are memory mapped by the Cache Manager into the system cache, eliminating the registry size limit. The registry size is now limited only by the available disk space. The System hive still has a maximum size, but it has been raised from 12 MB to 200 MB, eliminating the issue previous Windows versions faced^[37] of being unable to boot because of a large or fragmented System hive. The Configuration Manager has been updated to minimize the registry's memory footprint and lock contention, reduce fragmentation and thus page faults when accessing the registry, and improved algorithms to speed up registry query processing. An in-memory security cache eliminates redundant security descriptors.

Windows XP supports cross user session debugging, attaching the debugger to a non-crashing user-mode program, dumping the process memory space using the dump command, and then detaching the debugger without terminating it. Debugging can be done over a FireWire port and on a local system. The debug heap can be disabled and the standard heap be used when debugging.

Windows XP introduces support for Vectored Exception Handling. Vectored Exception Handling is made available to Windows programmers using languages such as C++ and Visual Basic. VEH does not replace Structured Exception Handling (SEH), rather VEH and SEH coexist with VEH handlers having priority over SEH handlers. Compared with SEH, VEH works more like a traditional notification callback scheme.

Applications can intercept an exception by calling the AddVectoredExceptionHandler API to watch or handle all exceptions. Vectored handlers can be chained in order in a linked list and they aren't tied to the stack frame, so they can be added anywhere in the call stack unlike SEH's try/catch blocks.

Heap leak detection can be enabled when processes exit and a debugger extension can be used to investigate leaks. Also introduced is a new heap performance-monitoring counter. Windows XP introduces a new low fragmentation heap policy (disabled by default) which allocates memory in distinct sizes for blocks less than 16KB to reduce heap fragmentation. The Low Fragmentation Heap can be enabled by default for all heaps using the LFH Heap Enabler utility.^[38]

There are new APIs for IRP cancellation and registering file system filter callbacks to intercept the OS fast I/O functions. In low memory conditions, "must succeed" calls are denied, causing a slowdown but preventing a bug check. I/O is throttled to fetch only one memory page at a time increasing overall scalability.

Windows XP includes NTFS 3.1, which expands the Master File Table (MFT) entries with a redundant MFT record number, useful for recovering damaged MFT files. The NTFS conversion utility, Convert.exe, supports a new /CvtArea switch so that the NTFS metadata files can be written to a contiguous placeholder file, resulting in a less fragmented file system after conversion. NTFS 3.1 also supports symbolic links although there are no tools or drivers shipped with Windows XP to create symbolic links.^[39]

Windows XP introduces the ability to mount NTFS read-only volumes. There are new APIs to preserve original short file names, to retrieve a list of mount points (drive letters and mounted folder paths) for the specified volume, and to enable applications to create very large files quickly by setting the valid data length on files without force-writing data with zeroes up to the VDL (SetFileValidData function). For instance, this function can be used to quickly create a fixed size virtual machine hard disk.^[40] The default access-control lists for newly created files are read-only for the Users group and write permissions are given only to the Administrators group, the System account and the owner.

The ability to boot in 30 seconds was a design goal for Windows XP, and Microsoft's developers made efforts to streamline the system as much as possible; The Logical Prefetcher is a significant part of this; it monitors what files are loaded during boot, optimizes the locations of these files on disk so that less time is spent waiting for the hard drive's heads to move and issues large asynchronous I/O requests that can be overlapped with device detection and initialization that occurs during boot. The prefetcher works by tracing frequently accessed paged data which is then used by the Task Scheduler to create a prefetch-instructions file at %WinDir%\Prefetch. Upon system boot or the launch of an application, any data and code in the trace that is not already in memory is prefetched from the disk. The previous prefetching results determine which scenario benefited more and what should be prefetched at the next boot or launch. The prefetcher also uses the same algorithms to reduce application startup times. To reduce disk seeking even further, the Disk Defragmenter is called in at idle time to optimize the layout of these specific files and metadata in a contiguous area. Boot and resume operations can be traced and analyzed using Bootvis.exe.

Windows XP includes a Fast Logon Optimization feature that performs logon asynchronously without waiting for the network to be fully initialized if roaming user profiles are not set up.^[41] Use of cached credentials avoids delays when logging on to a domain. Group Policy is applied in the background, and startup or logon scripts execute asynchronously by default.

Windows XP reconciles local and roaming user profiles using a copy of the contents of the registry. The user is no longer made to wait as in Windows 2000 until the profile is unloaded. Windows XP saves locked registry hives with open keys after 60 seconds so that roaming profile changes can be saved back to the server. The problem left is that the computer cannot recover the memory the profile uses until it can be unloaded. To make sure the user profiles are completely reconciled correctly during logoff, Microsoft has released the User Profile Hive Cleanup service for Windows XP, which they later included in Windows Vista.^[42][43]

Windows XP offers enhancements for usability, resilience against corruption and performance of roaming user profiles.^[44] There are new Group Policies to prevent propagation of roaming user profile changes to the server, give administrators control over users' profile folders and preventing the use of roaming user profiles on specific computers. To accommodate the scenario where an older profile would overwrite a newer server profile due to Windows XP's Fast Logon feature, Windows XP ensures in such a situation that the user registry hive is copied from the server to the local profile.

Deletion of profiles marked for deletion at the next logoff does not fail for locked profiles. For workgroup computers, Windows XP no longer deletes the profiles of users belonging to the Guests group.

Windows XP includes some changes to the behavior of Offline Files. The Offline Files Client-Side Cache can now be encrypted with Encrypting File System. Shared folders from DFS namespaces can be made available offline.^[45] Also, roaming user profiles can be synchronized with the server even if Offline Files has marked the server as unavailable.^[46]

Beginning with Windows XP, folders redirected to the network are automatically made available offline using Offline Files, although this can optionally be disabled through Group Policy.

For older Windows NT 4.0 and earlier systems with legacy directory structure, Windows XP allows redirecting the My Documents folder to their home directory.

In Windows XP, there are some improvements made to System Restore compared to Windows Me.^[47] System Restore uses a copy-on-write file system filter driver for taking snapshots. In Windows XP, System Restore is configurable per volume and the data stores are also stored per volume. On NTFS volumes, the Restore Points are stored using NTFS compression and protected using ACLs. A Disk Cleanup handler allows deleting all but the most recent Restore Point. Besides the Registry hives and system files, COM+ and WMI databases and the IIS metabase can also be restored. System Restore supports Group Policy. System Restore in Windows XP also works without issues with EFS-encrypted files.

Automated System Recovery is a feature that provides the ability to save and restore Windows and installed applications, the system state, and critical boot and system files from a special backup instead of a plain reinstall.^[48] ASR consists of two components - backup and restore. The Backup portion located in NTBackup backs up the system state (Windows Registry, COM+ class registration database, Active Directory and the SYSVOL directory share), and the volumes associated with operating system components required to start Windows after restore as well as their configuration (basic or dynamic).^[49] The Restore portion of ASR is accessed by pressing F2 from Windows XP Text mode Setup.^[50] Automated System Recovery can even restore programs and device drivers if they are added to the ASR Setup information disk.^[51] ASR does not restore data files.

A common issue in previous versions of Windows was that users frequently suffered from DLL hell, where more than one version of the same dynamically linked library (DLL) was installed on the computer. As software relies on DLLs, using the wrong version could result in non-functional applications, or worse. Windows 98 Second Edition and Windows 2000 partially solved this problem for native code by introducing side-by-side component sharing and DLL/COM redirection. These operating systems allowed loading a private version of the DLL if it was placed in the application's folder by the developer, instead of the system directory and must be registered properly with the system.

Windows XP improves upon this by introducing side-by-side assemblies for COM+ 2.0, .NET, COM classic, and Win32 components (C Runtime, GDI+, Common Controls). The technology keeps multiple digitally signed versions of a shared DLL in a centralized WinSxS folder and runs them on demand to the appropriate application keeping applications isolated from each other and not using common dependencies. Manifests and the assembly version number are used by the OS loader to determine the correct binding of assembly versions to applications instead of globally registering these components. To achieve this, Windows XP introduces a new mode of COM object registration called Registration-free COM (or RegFree COM). It allows Component Object Model (COM) components to store activation metadata and CLSID (Class ID) for the component without using the registry. Instead, the metadata and CLSIDs of the classes implemented in the component are declared in an assembly manifest (described using XML), stored either as a resource in the executable or as a separate file installed with the component.^[52] This allows multiple versions of the same component to be installed in different directories, described by their own manifests, as well as XCOPY deployment.^[53]

During application loading, the Windows loader searches for the manifest.^[54] If it is present, the loader adds information from it to the activation context^[53] When the COM class factory tries to instantiate a class, the activation context is first checked to see if an implementation for the CLSID can be found. Only if the lookup fails is the registry scanned.^[53]

Windows Error Reporting collects and offers to send post-error debug information (a memory dump) using the internet to the developer of an application that crashes or stops responding on a user's desktop. No data is sent without the user's consent. When a dump (or other error signature information) reaches the Microsoft server, it is analyzed and a solution is sent back to the user if one is available. Windows Error Reporting runs as a Windows service and can optionally be entirely disabled. Software and hardware manufacturers may access their error reports using Microsoft's Winqual program.^[55] Software and hardware manufacturers can also close the loop with their customers by linking error signatures to Windows Error Reporting Responses. This allows distributing solutions as well as collecting extra information from customers (such as reproducing the steps they took before the crash) and providing them with support links.

On old versions of Windows, when users upgrade a device driver, there is a chance the new driver is less stable, efficient or functional than the original. Reinstalling the old driver can be a major hassle and to avoid this quandary, Windows XP keeps a copy of an old driver when a new version is installed. If the new driver has problems, the user can return to the previous version. This feature does not work with printer drivers.^[56]

• Windows Driver Protection blocks known problematic drivers from installing or loading^[57]
• The Driver Verifier introduced in Windows 2000 is a tool that replaces the default operating system subroutines with ones that are specifically developed to catch device driver bugs.^[58] Once enabled, it monitors and stresses drivers to detect illegal function calls or actions that may be causing system corruption. In Windows XP, new verification options have been added for DMA, I/O, SCSI and deadlock detection to Driver Verifier. Driver Verifier Manager, a GUI is introduced for Driver Verifier and includes the ability to automatically verify unsigned drivers.
• Last Known Good Configuration in Windows 2000 restored the hardware configuration in the registry control set indicated by the LastKnownGood key instead of the default. In Windows XP, it is extended to support restoring the device drivers too of the last working configuration, should a newly installed device driver make Windows unbootable.

As Windows XP merged the consumer and enterprise versions of Windows, it needed to support applications developed for the popular and consumer-oriented Windows 9x platform on the Windows NT kernel. Microsoft addressed this by improving compatibility with application-specific tweaks and shims and by providing tools such as the Application Compatibility Toolkit (AppCompat or ACT)^[59] to allow users to apply and automate these tweaks and shims on their own applications.^[60] Users can script the Compatibility Layer using batch files.^[61] Windows XP Setup also includes a compatibility checker that warns users - before setup begins - of incompatible applications and device drivers or of applications that may need reinstallation.^[62]

The RTM release of Windows XP includes Windows Media Player version 8 (officially called Windows Media Player for Windows XP) and Windows Media 8 codecs. Windows Media Player for Windows XP introduced ID3 support for MP3s, editing media information from within the Library, adding lyrics for MP3 or WMA tracks, file name customization when ripping, new visualizations, support for HDCDs, ability to lock down the player in a corporate environment and DVD playback support (when appropriate codecs are installed separately).^[63] Windows Media Player also incorporates newer hardware support for portable devices by means of the Media Transfer Protocol and the User-Mode Driver Framework-based Windows Portable Devices API.

The original RTM release of Windows XP included Windows Movie Maker 1.1 which added non-compressed DV AVI recording of digital video sources. Windows Movie Maker 2 introduced numerous new transitions, effects, titles and credits, a task pane, resizable preview window with dimensions, improved capture and export options, an AutoMovie feature, saving the final video back to tape and custom WMV export profiles.^[64]

Windows XP includes advances in Broadcast Driver Architecture for receiving and capturing analog and digital TV broadcasts complete with signal demodulation, tuning, software de-multiplexing, electronic program guide store, IP data broadcasting etc.^[65]

Windows XP includes improved FireWire (IEEE 1394) support (DVCPRO25 – 525-60 and 625-50) for digital video cameras and audio video devices.^[66] It introduces MSTape, a WDM driver for D-VHS and MPEG camcorder devices.^[67]

DirectShow 8 introduces the Video Mixing Renderer-7 (VMR-7) filter which uses DirectDraw 7 for video rendering, replacing the Overlay Mixer. VMR-7 can mix multiple streams and graphics with alpha blending, allowing applications to draw text (such as closed captions) and graphics (such as channel logos or UI buttons) over the video without flickering, and support compositing to implement custom effects and transitions.^[68] VMR-7 also supports source color keying, overlay surface management, frame-stepping and improved multiple-monitor support. VMR-7 features a "windowless mode" for applications to easily host video playback within any window and a "renderless playback mode" for applications to access the composited image before it is rendered. DirectX 9 introduced the VMR-9 which uses Direct3D 9 instead of DirectDraw, allowing developers to transform video images using the Direct3D pixel shaders.^[69]

DirectShow 8 includes AVStream, a multimedia class driver for video-only and audio-video kernel streaming.

• Windows Media Encoder 9 Series allows encoding Windows Media 9–based content.
• Installing Windows Media Connect or Windows Media Player 11 adds a UPnP-based streaming media server.

Windows XP provides new and/or improved drivers and user interfaces for devices compared to Windows Me and 98.

Beginning with Windows XP Service Pack 1, generic USB 2.0 Enhanced Host Controller Interface drivers are installed.^[70] Windows XP also adds support for USB device classes such as Bluetooth, USB video device class, imaging (still image capture device class) and Media Transfer Protocol with Windows Media Player 10.^[71]

For mass storage devices, Windows XP introduces hardware descriptors to distinguish between various storage types so that the operating system can set an appropriate default write caching policy.^[72] For example, for USB devices, it disables write caching by default so that surprise removal of these devices do not cause data loss. Device Manager provides a configuration setting whether to optimize devices for quick removal or for performance.

Windows XP supports both TWAIN as well as Windows Image Acquisition-based scanners. Windows Image Acquisition in Windows XP adds support for Automatic document feeder scanners, scroll-fed scanners without preview capabilities and multi-page TIFF generation.^[73] For WIA video, a Snapshot filter driver is introduced which allows still frames to be captured from the video stream.

The Scanner and Camera Wizard based on Windows Image Acquisition and other common dialogs for WIA devices have been improved in Windows XP to show the media information and metadata, rotate images as necessary, categorize them into subfolders, capture images and video in case of a still or video camera, crop and scan images to a single or multi-page TIFF in case of a scanner. The Picture Transfer Protocol (PTP) implementation has been updated to support all mandatory and optional commands in the PTP standard, and object tree support which allows secondary files associated with a parent file to be grouped and transferred concurrently.^[73] Windows Media Player 10 also adds the Media Transfer Protocol for transferring media content from portable devices. Thus, for digital cameras, Windows XP supports acquiring photos using any of either WIA, PTP, USB Mass Storage Class or MTP protocols depending on what the camera manufacturer supports.

Windows XP includes technology from Roxio which allows users to directly burn files to a compact disc through Windows Explorer. Previously, end users had to install CD burning software. In Windows XP, CD and DVD-RAM (FAT32 only for DVD-RAM) burning has been directly integrated into the Windows interface. Data discs are created using the Joliet and ISO 9660 file systems and audio CDs using the Redbook standard.^[74] To prevent buffer underrun errors, Windows XP premasters a complete image of files to be burnt and then streams it to the disc burner.^[74] Users can burn files to a CD in the same way they write files to a floppy disk or to the hard drive via standard copy-paste or drag and drop methods. The burning functionality is also exposed as an API called the Image Mastering API. Windows XP's CD burning support does not do disk-to-disk copying or disk images, although the API can be used programmatically to do these tasks. Creation of audio CDs is integrated into Windows Media Player. Audio CDs are burnt using track-at-once mode.^[74] CD-RW discs can be quick erased.

API support can be added to Windows XP for burning DVDs and Blu-ray Discs (Mastered-style burning and UDF) on write-once and rewritable DVD and Blu-ray media by installing the Windows Feature Pack for Storage which upgrades IMAPI to version 2.^[75][76] Note that this does not add DVD or Blu-ray burning features to Windows Explorer but third-party applications can use the APIs to support DVD and Blu-ray burning.

• Support for the Simple Boot Flag (SBF) specification which tells the BIOS to bypass or minimize startup checks if the operating system is Plug and Play capable.
• Wake-on-Battery support so that the system has time to power off or hibernate
• CardBus Wake-on-LAN support
• Wake on LAN can be configured to limit wake up packets to just magic packets from the Power management tab of the NIC property page in Device Manager.
• LCD dimming when on battery power
• Processor power and performance control including C-state (run in lower power state when idle) and throttling^[77]
• USB selective suspend feature
• Significantly noticeable fast boot and resume from hibernation^[78] compared to previous Windows versions owing to the boot loader caching file and directory metadata sequentially and in large chunks in a most recently used manner, overlapping device and network initialization, faster boot disk enumeration and class drivers being initialized asynchronously. Hibernation is faster as memory pages are compressed using an improved algorithm, compression is overlapped with disk writes, unused memory pages are freed and DMA transfers are used during I/O.
• Faster resume from standby as the algorithm used by the Power Manager for notifying hardware and software of power state changes by dispatching power IRPs has been rewritten to maximize parallelism, important system drivers (PCMCIA, keyboard, mouse) have been rewritten to eliminate blocking interactions,^[79] and worker thread stacks are locked in memory to prevent interruptions with power operations.
• Built-in support for processor power management technologies such as Intel SpeedStep and AMD PowerNow!.

• Support for audio devices based on the Intel High Definition Audio specification by means of a Universal Audio Architecture (UAA) class driver.
• Multichannel audio output and playback of additional audio formats. Volume can be set for each speaker in a multichannel configuration.
• KMixer audio sampling rate supports a maximum of 200 kHz beginning with Windows XP SP1 compared to earlier versions of Windows.^[80]
• Restriction on number of MME/WinMM device interfaces (waveIn, waveOut, midiIn, midiOut, mixer, and aux) is raised from 10 to 32.^[81][82]
• Hardware acceleration of DirectSound capture effects^[83] These include Acoustic Echo Cancellation for USB microphones, noise suppression and array microphone support.
• USB audio devices support GFX (Global Effects Filters).^[84]
• Sound Blaster 2.0 emulation support in NTVDM
• Windows XP sets the volume levels on wave, CD Audio and MIDI sliders to 0 dB of attenuation. This prevents signal resolution degradation.^[85]

Windows XP includes FireWire 800 support (1394b) beginning with Service Pack 1.^[86]

As mentioned in the above section, Windows XP includes improved support for FireWire cameras and audio video devices.^[66] S/PDIF audio and MPEG-2 video streams are supported across FireWire from audio video receivers or set-top boxes, DVD or D-VHS, speakers, or TV transmissions.^[66] Windows XP supports the AV/C (IEC 61883 protocol for isochronous real-time data transfer for audio-video applications.^[66] Windows XP also allows non-FireWire devices to be exposed as virtual FireWire devices. Direct memory access over the 1394 bus from the host to the target allows kernel debugging over FireWire.

Finally, there is support for TCP/IP networking and Internet Connection Sharing over the IEEE 1394 bus.^[87]

• Details tab in Device Manager which displays various device identification strings such as device instance ID, hardware ID, service name, filters, firmware revision, power state mappings and capabilities etc.^[88]
• Windows XP's user interface for Plug and Play changed with all messages being shown in the notification area as balloon tips.
• The read-only attribute of files and folders is automatically removed when copying files from optical media using Windows Explorer.
• Improved mouse pointer ballistics.^[89]
• DualView for multi-monitor setups.^[90] DualView allows two monitors to host the Windows desktop, while being driven off of a single display adapter.
• Support for reading UDF 2.01 upgradeable to UDF 2.50 by installing Windows Feature Pack for Storage.^[76]
• 48-bit LBA support for ATA/ATAPI disk drives^[91] and generic drivers for UltraDMA Mode 5 and 6 support beginning with Windows XP SP1.
• Executing user applications directly from ROM.
• Support for the exFAT file system can be added by installing KB955704.^[92]
• Supports VBE display if vendor-specific graphics driver not installed, or in the safe mode.
• GDI can utilizes OpenGL 1.0 for 2D acceleration if vendor-specific graphics driver not installed, or in the safe mode.

Windows XP includes Windows Script Host 5.6, a major update to the WSH environment, which includes an improved object model to reduce boilerplate code, stronger security and several other improvements.^[93]

A new XML-based file format, the Windows Script File format (.WSF) has been introduced besides .VBS and .JS which can store in an XML node in the same file, extra information besides script code, such as digital signature blocks, runtime directives or instructions to import external code.^[93] The WSF schema can include jobs wrapped each by a unique <job> tag and an outer <package> tag. Tags in a WSF file allow including external files, importing constants from a TLB, or storing the usage syntax in the <Runtime> element and displaying it using the new ShowUsage method, or when invoked by the /? switch.^[93] The WSF format also supports hosting multiple WSH scripting languages, including cross function-calls. The WshShell object now supports a 'CurrentDirectory' read-write method.^[93]

Scripts can now be digitally signed as well as verified programmatically using the Scripting.Signer object in a script itself, provided a valid certificate is present on the system.^[93] Alternatively, the signcode tool from the Platform SDK, which has been extended to support WSH filetypes, may be used at the command line.^[94] The VerifyFile method can be used to authenticate the embedded signature's validity and check the script for modifications after signing. WSH can thus decide whether or not to execute the script after verification.^[93] Code stored in an in-memory string can also be signed by using the Sign method. The signature block is stored in a commented section in the script file for backward compatibility with older WSH versions.^[93]

By using Software Restriction Policies supported in Windows XP and later, a system may also be configured to execute only those scripts which have been digitally signed, thus preventing the execution of untrusted scripts.^[95]

Local scripts can also run on a remote machine with the new WScript.WshController object, which is powered by DCOM.^[93] Remote WSH can be enabled through a Group Policy Administrative Template or registry.^[93] Remote scripts always run through wscript and are loaded into the remote machine's Server process so they run non-interactively by default, but can be configured using DCOMCNFG to run in a security context that allows them to display the user interface.^[93] When the WSH automation server loads, an instance of the WshRemote object is created but the script runs only after calling the Execute method.^[93] Any external files called by the remote script must be located on the remote machine in the directory path specified by the Exec method. The remote script can be monitored by using the Status property.^[93]

WSH 5.6 introduces the Exec method for the WshShell object to execute command-line console applications and has access to the standard I/O streams (StdIn, StdOut, and StdErr) of the spawned process.^[93]

In earlier versions of Windows Script, to use arguments, one had to access the WshArguments collection object which could not be created externally and required that the person running the script know the order of the arguments, and their syntax and values.^[96] WSH 5.6 introduces named arguments on the command line which follow a /string:value or Boolean convention defined in 'Runtime' tag and are recognized irrespective of their order on the command line. Named arguments are grouped in the Named collection object and have the usual methods like Item, Count, Length as well as an Exists method.^[93] The 'ShowUsage' method for the WshArguments object mentioned earlier shows the argument information in a message box.^[93]

Windows XP includes a ScriptPW.Password COM automation object, implemented in the scriptpw.dll file which can be used to mask sensitive information like passwords from command line scripts.^[93]

Users can log into Windows XP Professional remotely through the Remote Desktop service. It is built on Terminal Services technology (RDP), and is similar to "Remote Assistance", but allows remote users to access local resources such as printers.^[97] Any Terminal Services client, a special "Remote Desktop Connection" client, or a web-based client using an ActiveX control may be used to connect to the Remote Desktop.^[98] (Remote Desktop clients for earlier versions of Windows, Windows 95, Windows 98 and 98 Second Edition, Windows Me, Windows NT 4.0, or Windows 2000 have been made available by Microsoft.^[99] This permits earlier versions of Windows to connect to a Windows XP system running Remote Desktop, but not vice versa.)

There are several resources that users can redirect from the remote server machine to the local client, depending upon the capabilities of the client software used. For instance, "File System Redirection" allows users to use their local files on a remote desktop within the terminal session, while "Printer Redirection" allows users to use their local printer within the terminal session as they would with a locally or network shared printer. "Port Redirection" allows applications running within the terminal session to access local serial and parallel ports directly, and "Audio" allows users to run an audio program on the remote desktop and have the sound redirected to their local computer. The clipboard can also be shared between the remote computer and the local computer. The RDP client in Windows XP can be upgraded to 7.0. The Remote Desktop Web Connection component of Internet Information Services 5.1 also allows remote desktop functionality over the web through an ActiveX control for Internet Explorer.^[100]

Remote Assistance allows a Windows XP user to temporarily take over a remote Windows XP computer over a network or the Internet to resolve issues.^[101][102] As it can be a hassle for system administrators to personally visit the affected computer, Remote Assistance allows them to diagnose and possibly even repair problems with a computer without ever personally visiting it. Remote Assistance allows sending invitations to the support person by email, Windows Messenger or saving the invitation as a file. The computer can be controlled by both, the support person connecting remotely as well as the one sending the invitation. Chat, audio-video conversations and file transfer are available.

Windows XP introduces Fast User Switching^[103] and a more end user friendly Welcome Screen with a user account picture which replaces the Classic logon prompt. Fast user switching allows another user to log in and use the system without having to log out the previous user and quit his or her applications. Previously (on both Windows Me and Windows 2000) only one user at a time could be logged in (except through Terminal Services), which was a serious drawback to multi-user activity. Fast User Switching, like Terminal Services, requires more system resources than having only a single user logged in at a time and although more than one user can be logged in, only one user can be actively using their account at a time. This feature is not available when the Welcome Screen is turned off, such as when joined to a Windows Server Domain or with Novell Client installed.^[102][104] Even when the Welcome screen is enabled, users can switch to the Classic logon by pressing Ctrl+Alt+Del twice at the Welcome screen.^[105]

Windows XP introduced Windows Installer (MSI) 2.0. Windows Installer 2.0 brought major improvements such as installation and management of side by side and CLR assemblies, sandboxing MSI custom actions, improved event logging and hiding sensitive information in log files, per-user program isolation, digital signatures, improved patching (more robust patch conflict resolution and reduced unnecessary unversioned file copying and source prompts), Terminal Server support and integration with System Restore and Software Restriction Policies.^[106] Windows XP can be updated to Windows Installer 4.5.^[107]