Windows XP

Windows XP, codenamed Whistler, is an operating system developed by Microsoft, released in October 2001. It is a direct upgrade to its predecessors, Windows 2000 Professional and Windows Me, and is available for any devices running Windows NT 4.0, Windows 98, Windows 2000 or Windows Me that meet the new Windows XP system requirements. It is the final client version of Windows to support computers without ACPI and the last client version of Windows NT to use NTLDR to boot the system. Unlike prior releases, Windows XP no longer ships with a set of bootable floppy disks by default. The boot disks had to be created manually using a tool, which could be downloaded from the Microsoft web page. There were two individual versions of the tool to create boot disks for either XP Home Edition or Professional.

It is one of Microsoft's longest-lasting operating systems, with almost 13 years of support (both mainstream and extended) and still runs on 0.46% of computers worldwide as of February 2023. Mainstream and extended support ended on 14 April 2009 and 8 April 2014 respectively. Despite this, a total of three out-of-band updates were released for the operating system, fixing the following issues:
 * a high-risk Internet Explorer vulnerability; released in 2014
 * mitigations for the ETERNALBLUE SMB vulnerability, notably used by the WannaCry ransomware; released in 2017
 * mitigations for the BlueKeep RDP vulnerability; released in 2019

Windows XP lost full support on 9 April 2019 when the extended lifecycle for its last remaining derivative, Windows Embedded POSReady 2009, had ended.

User interface
Windows XP received a major UI overhaul during development through the introduction of visual styles. Users could change the way windows and buttons looked with the new Luna visual style. It had three color schemes, which were based on blue, green, and silver. Users were given the ability to switch back to the older Windows Classic visual style from previous versions of Windows and customize the preset Windows Classic color schemes. The Luna visual style was the subject of mild criticism, with some consumers describing the visual style as bearing a resemblance to a "Fisher-Price toy".

Windows XP saw the introduction of ClearType anti-aliasing, which allows for better text legibility on desktop computers with LCD-TFT monitors and laptops. As the feature had negatively affected CRT monitors, it was not enabled by default.

Windows Explorer received a major overhaul in its design and functionality with the introduction of the task pane which presents the user with a list of actions that a user can take depending on the selected item. Search Companions were also introduced to make searching more easier and there are four search characters available; Rover, Merlin, Earl and Courtney. They utilize the Microsoft Agent technolgy which is also used for the Office assistants. However, the classic search pane can still be restored by editing the registry. The filmstrip view has also been added, which allows to display thumbnails right from within the explorer. Metadata of files can also be viewed from the properties page as well. Support for creating and opening compressed folders and cabinet files was also added along with the ability to burn CDs and DVD-RAM discs.

To improve boot times and program launch times, prefetching was added and it accomplishes this by caching files that are needed by an program to RAM during the program's launch, thus consolidating disk reads and reducing disk seeks.

The compatibility modes were also added and are now activated out of the box. This feature allows users to run older programs by selecting an earlier version of Windows that the program previously ran on. This basically tricks the program into thinking that it is running on an older version of Windows. The compatibilty modes can be set for a program through its properties or by launching the Program Compatibility Wizard located in the Help and Support Center.

A new login screen was also introduced, which allows easier management of multiple accounts, though it only allowed five accounts as maximum and only worked if the computer joined a workgroup. Along with this, fast user switching was added, which allows users to login into the computer without having existing users to close out of their programs and log out. Fast user switching required the new login screen to be enabled. The legacy login prompt from Windows 2000 was still available and was needed if the computer joined a domain instead of a workgroup.

A DRM technology called Windows Product Activation was added which requires the user to activate their copy of Windows XP as a means of enforcing the relevant provisions of the license agreement about using the product on multiple computers. Activation could be done over the internet or over the telephone. If the user does not activate Windows XP after 30 days of installation, the user will be unable to login to Windows unless it is activated. A unique ID is assigned to the computer after activation and if the user makes significant changes to the hardware, the activation is voided and the operating system must be re-activated.

The taskbar is locked by default for new user accounts, to prevent accidental resizing or moving of the taskbar and/or the toolbars. Multiple instances of an application are grouped automatically and inactive tray area icons are hidden automatically, to prevent cluttering of the taskbar.

A new Start menu with two columns was introduced, which has the one column for pinned or recently opened apps and docs and the other one with shortcuts to certain places in the system. The user name and the new user picture are displayed at the top, while the buttons for logging off, undocking or shutting down the computer are located at the bottom. It is designed for use with large screens and the Luna theme, but it also can be used with the Windows Classic one. Additionally, the user can revert to the classic Start menu, where, apart from new shortcuts, icons and banner, almost nothing has been changed.

Applications and components

 * Internet Explorer 6 was introduced and can be updated up to Internet Explorer 8.
 * Along with this, Outlook Express was updated to version 6 and Windows Address Book was added.
 * MSN Explorer was introduced to the NT line of Windows.
 * Windows Messenger 4.0 was added. It was upgraded to version 4.7 in Windows XP SP2 and could be used simultaneously with later versions of MSN Messenger or Windows Live Messenger.
 * MSXML 3.0 was introduced. It was upgraded to MSXML 6.0 SP2 in Windows XP SP3.
 * Remote Assistance was added which allows a user to view or control a remote Windows computer over a network or the Internet to resolve issues.
 * Windows Picture and Fax Viewer was added, replacing Imaging.
 * The Language Bar was added. It appears if more than one keyboard layout has been installed, though it is minimized to the taskbar by default.
 * Windows Media Player 8 was introduced. It was updated to version 9 in Windows XP SP2, and can be updated to version 11.
 * Windows Movie Maker 1.1 was introduced. It was upgraded to Windows Movie Maker 2.1 in Windows XP SP2.
 * The Terminal Services Client was renamed to Remote Desktop Connection.
 * The Fax console was added.
 * The Text Services Framework was introduced.
 * Windows NetMeeting 3.01 was introduced and can be updated to 3.02.
 * WordPad now has full Unicode support.
 * Desktop Cleaning Wizard was added.
 * DirectX 8.1 was introduced. It was upgraded to DirectX 9.0c in Windows XP SP2.
 * Windows Error Reporting was introduced.
 * The ability to easily roll back a device driver to an old version was added.
 * Wireless Zero Configuration was introduced.
 * Password reset disks can be created to reset the user account password.
 * Windows Script Host 5.6, upgraded to 5.7 in SP3.
 * Automated System Recovery replaced the Emergency Boot Disk as recovery option, though it is only available in Windows XP Professional and other SKUs based on it.

Deprecations

 * Windows XP drops the ability to upgrade from both Windows NT 3.51 and Windows 95, requiring at least Windows 98 or Windows NT 4.0. SP2 also drops the ability to upgrade from the original release of Windows 98 and Windows NT 4.0, as it now requires Windows 98 SE, Windows 2000 or Windows Me for an upgrade. SP3 also drops the ability to upgrade from Windows 9x, requiring at least Windows 2000.
 * Links to Phone Dialer and Windows NetMeeting have been removed from the Start menu. They can still be accessed and used by launching them directly (via  and  ).
 * The AppleTalk protocol was completely removed and is no longer available for download from Microsoft.
 * WebTV for Windows was removed. MSN TV is available as a replacement.
 * The QuickEdit and Insert modes in the Command Prompt have been disabled by default.
 * The Small icons view was removed from Windows Explorer.
 * Deluxe CD Player, which was also first part of Microsoft Plus! 98 before being included in Windows 2000, and DVD Player, which in Windows 98 and Windows 2000 plays DVDs if a hardware-based MPEG decoder is present, have both been removed, as CD/DVD playback functionality moved to Windows Media Player.
 * Imaging for Windows was removed and replaced by Windows Picture and Fax Viewer.
 * The Directory icon was removed from My Network Places.
 * The NetDDE and NetBEUI protocols are no longer installed by default but can still be manually installed from the Windows XP CD-ROM.
 * The DLC network protocol is no longer included by default.
 * In Windows XP Service Pack 2, the following raw socket functionality was removed: sending TCP network packets, sending UDP packets with invalid source network addresses, and associating local addresses.
 * The Microsoft POSIX and OS/2 subsystems were removed. Windows Services for UNIX is available as a replacement.
 * The DriveSpace utility was removed in favor of native NTFS compression.
 * The "Starting Windows..." message before the boot screen, which was present in Windows 2000, was removed, only leaving the progress bar on some configurations.
 * The progress bar on the boot screen is now an indeterminate progress bar and not determinate like with Windows 2000.
 * The Line Up Icons command on the desktop was replaced by the Align to Grid command.
 * The Customize This Folder wizard was removed.
 * In Windows XP SP2, Program Manager was replaced with a compatibility stub that redirects to Windows Explorer.
 * Starting with Internet Explorer 6 Security Version 1, Media Bar, which replaced the Radio Toolbar in the original and Service Pack 1 releases of Internet Explorer 6, was removed.
 * Support for TCP half-open connections was removed in Service Pack 2 of Windows XP. Background message compaction was also removed from Outlook Express 6. Outlook Express in Service Pack 2 automatically compacts messages every hundredth time it is run.
 * The radio edit of David Byrne's "Like Humans Do", as previously included in the original and Service Pack 1 releases of Windows XP, was removed in Windows XP SP2.
 * The Windows Movie Maker Sample File (generated by Windows Movie Maker 1.1 when it is started for the first time), which consisted of clips of a male child riding a tricycle and playing in a playground, was removed in Windows XP SP2.
 * The unique boot screens in the original and Service Pack 1 releases of Windows XP that have a green progress bar for Home Edition and a blue progress bar for Professional, Embedded, Tablet PC Edition and Media Center Edition, were removed in Service Pack 2 of Windows XP and was replaced with a single generic "Windows XP" boot screen with a blue progress bar.
 * The Address bar toolbar was removed from the taskbar in Service Pack 3 of Windows XP. Windows Desktop Search is touted as a replacement.
 * The ability to use boot disks to boot into setup was removed in Windows XP SP3.
 * The option to display the special Internet Explorer icon on the desktop was removed in Windows XP SP3.
 * The ability to install service packs cumulatively is no longer available in Windows XP SP3 as it requires at least Service Pack 1 to be installed first (Service Pack 2 in the cases of the original Windows XP Media Center Edition and Windows XP Media Center Edition 2005). Cumulative slipstreaming, however, is still possible and supported.
 * The Energy Star logo in the Display Properties dialog, first introduced in Windows 95, was removed in Windows XP SP3.
 * Although Media Center Edition is based upon the Professional edition, domain support is unavailable. Microsoft states that this is due to Windows Media Center Extenders requiring fast user switching. The exceptions to this are if it is selected during installation or already in use before an upgrade, but leaving the domain will still disable the feature.
 * The hidden Windows Media Player 6.4 was removed in Windows XP Media Center Edition 2005.

Editions

 * Starter Edition: Intended for emerging markets utilizing low-cost PCs, and was first introduced in 2004. It cannot launch more than 3 programs at a time and included an artificial installed memory limitation of up to 512 MB RAM.
 * Home Edition: This edition is for home and personal users who do not need to use corporate network, security, and management features (such as joining domain networks, file encryption, Remote Desktop Connection, group policies, etc.) This version can address up to 4 GB of RAM, and it only supports a single physical processor (though multiple cores and threads are supported).
 * Professional: The mainstream high-end version, sold alongside Home Edition. It supports up to two physical processors and includes enterprise features such as group policy management, domain support and file encryption.
 * 64-Bit Edition: This was a special edition for Itanium-based computers. There were two releases, the first of which was released in 2001 and was based on Windows XP; the second of which was released in 2003 and was based on Windows Server 2003. Support for these versions was dropped in 2005.
 * Professional x64 Edition: This was the version for x86-64 processors based on Windows Server 2003. It was released in 2005.
 * Media Center Edition: This version is especially for Media Center-based PCs, and is not sold normally. System requirements are significantly higher than in other editions. This version includes the Windows Media Center application and includes new themes such as Royale, and additionally includes Microsoft Plus! features.
 * Embedded: Intended for the embedded hardware sector. Enterprises can create a customizable Windows XP Professional image through the use of an image builder utility, allowing them to add and remove features or drivers as needed and then later deployed to hardware built for specific solutions, such as point-of-sale terminals and automated teller machines.
 * Tablet PC Edition: This version was included in tablet computers from 2002-2007. It is the tablet-optimized version of Windows XP.
 * N, K and KN editions: The N version was made for the European markets and did not include Windows Media Player; the K version was made for the South Korean markets and included two shortcuts to Korean websites offering media player and messenger software by default, after a South Korean Fair Trade Commission ruling. The KN edition is the Korean counterpart to the N edition.

Marketing
Windows XP was initially marketed with the slogan Prepare to Fly, although it was later changed to Yes You Can as a direct result of several real-world terrorist attacks occurring on 11 September 2001. The TV advertisements used the music track Ray of Light from Madonna as background music. The initial marketing campaign was refreshed in 2004 with the release of Service Pack 2, with the slogan once again changed to Everything is Possible. This campaign ran until late 2006.

Myths and legends
No builds of Whistler ever used or even included the widespread startup and shutdown sounds. These originate from a Whistler theme from ThemeWorld, which includes an entire sound scheme of sounds from various sources such as Plus! 98, although these are not as widespread. The fake startup sound was made for the previous one, using Windows 98 Plus!'s World Traveler, Architecture shutdown sound, and PhotoDisc startup sound, and the final version using Windows 98's shutdown sound reversed, Windows 2000 build 1983.1 to build 2000.3's startup sound reversed, and the Next Level sound from a game titled Spring Weekend included in the Microsoft Entertainment Pack slowed down, while the shutdown sound is from BeOS, albeit down sampled.

In actuality, all builds up until 2485 use the same sounds as Windows 2000 and Me. Build 2481 introduced the sounds used in the final release (albeit in stereo and 44.1kHz), but they were not used by default at this point.

System requirements
According to Microsoft, Windows XP requires a Pentium processor running on 233 MHz, at least 64 MB of RAM, 1.5 GB of hard drive space, and a Super VGA or better display adapter. Windows XP drops full support for processors without the CPUID instruction, like the 486. Additionally, the HAL for the SGI Visual Workstation 320 and 540 is no longer included in Windows XP. Windows XP updates the default VGA driver to take advantage of VESA BIOS extensions, allowing true color display and resolutions in the default VGA driver, although this requires a graphics card that supports SVGA.

Source code leak
On 23 September 2020, the source code for the RTM builds of Windows XP Service Pack 1 and Windows Server 2003 leaked onto 4chan's /g/ board. As referenced within the original post, the code had been circulating in private circles for several years at most. Due to the incompleteness of both source code repositories, primarily within the activation functionalities, it is fair to assume that the disclosure had originated from a Microsoft Partner who had access to the source code rather than Microsoft themselves. The ability to glance into the groundwork of this operating system has led to some discoveries, an example being the checks for enabling the DirectUI-based Start Page from  being usable in build 2410.

Additional products in the source code
As Windows ships with numerous utilities, the source code to Windows XP SP1 and Windows Server 2003 additionally comes with the source code to many different components and utilities of Windows that could be installed separately:


 * .NET Framework 1.1 (Server 2003 only, including a file from an extremely early (~Feb 2002, although compiled in August) version of the Windows Presentation Foundation framework (the version is the .NET version, and 6.0.3699.0 would indicate a lower version than the RTM of .NET 1.0 in Feb 2002, 6.0.3705.0), and a .NET Version Information Utility from 1998).
 * Internet Explorer 6.0 SP1
 * NetMeeting 3.01
 * Microsoft UDDI Services 1.0 (an Internet service discovery platform)
 * DirectX 8.1
 * Windows Media Player 5.1 (but not 6.4 or 8/9)
 * Zone Internet Games (client and shared code) 1.2
 * Microsoft Speech API (SAPI) 5.1
 * Windows Update Agent v3 and v4