Windows XP Professional x64 Edition
Screenshot of Windows XP Professional x64 Edition running the Luna visual style, showing the start menu and the "About Windows" window
Developer	Microsoft
OS family	Windows NT
Working state	No longer supported
Source model	Closed-source Source-available (throughShared Source Initiative)
Initial release	April 25, 2005; 20 years ago (2005-04-25)[1]
Final release	Service Pack 2 with May 14, 2019 security update (5.2.3790.6787) / April 19, 2019; 6 years ago (2019-04-19)[2]
Kernel type	Hybrid (NT)
Default user interface	Graphical user interface
License	Proprietarycommercial software
Official website	Windows XP Professional x64 Edition overview (archived atWayback Machine)
Support status
Mainstream support ended on April 14, 2009[3] Extended support ended on April 8, 2014[3]

Windows XP Professional x64 Edition is anedition ofMicrosoft'sWindows XP operating system that supports thex86-64 architecture. It was released on April 25, 2005, alongside the x86-64 versions ofWindows Server 2003.

Windows XP Professional x64 Edition is designed to use the expanded 64-bit memory address space provided by the x86-64 64-bit extensions to the x86 IA-32 architecture,^[1] which was implemented byAMD as "AMD64", found in AMD'sOpteron,Athlon 64 chips (and in selectedSempron processors), and implemented byIntel as "Intel 64" (formerly known as IA-32e and EM64T), found in some of Intel'sPentium 4 and most of Intel's later chips since theCore series.

Windows XP Professional x64 Edition uses the same kernel and code tree as Windows Server 2003^[4] and is serviced by the same service packs.^[5] However, it includes client features of Windows XP such asSystem Restore,Windows Messenger,Fast User Switching, Welcome Screen,Security Center and games, of which Windows Server 2003 does not have.

During the initial development phases (2003–2004), Windows XP Professional x64 Edition was namedWindows XP 64-Bit Edition for 64-Bit Extended Systems^[6] and later asWindows XP 64-Bit Edition for Extended Systems, as opposed to64-Bit Edition for Itanium Systems forWindows XP 64-Bit Edition, as the latter was designed for theIA-64 (Itanium) architecture.^[7][8]

Windows XP Professional x64 Edition offers a number of new and updated features not found in the main 32-bit x86 versions of Windows XP:

• Internet Information Services (IIS) version 6.0, the same version that was included in Windows Server 2003, is included with Windows XP Professional x64 Edition. All other 32-bit editions of Windows XP have IIS v5.1.
• Windows Media Player version 10, the version that came with Windows Server 2003 Service Pack 1, is included with Windows XP Profesional x64 Edition.^[9] Windows XP Professional for x86 originally shipped with Windows Media Player version 8 from RTM to Service Pack 1 and later came with Windows Media Player 9 from Service Pack 2 onwards, withWindows XP Media Center Edition 2005 receiving Windows Media Player 10. Windows Media Player 11 is available for x86 versions of Windows XP Service Pack 2 or later.
• Internet Protocol Security (IPsec) features and improvements made in Windows Server 2003 were included with Windows XP Professional x64 Edition.^[10]
• Shadow Copy, a feature that automatically creates daily backups of files and folders, was first introduced in Windows Server 2003 and is available in Windows XP Professional x64 Edition.^{[11][further explanation needed]}
• Remote Desktop Services supports Unicode keyboard input, client-side time-zone redirection, GDI+ rendering primitives for improved performance, FIPS encryption, fallback printer driver, auto-reconnect and new Group Policy settings.^[12]
• Files and Settings Transfer Wizard supports migrating settings from both 32-bit and 64-bit Windows XP PCs.^[13]

Windows XP Professional x64 Edition is based on theWindows Server 2003 kernel and codebase, which is newer than 32-bit Windows XP (by about two years) and has improvements to enhance scalability.^[14] It also introducesKernel Patch Protection (also known as PatchGuard) to improve security by helping to eliminate rootkits.^[15]

The primary benefit of moving to 64-bit is the increase in the maximum allocatablerandom-access memory (RAM). 32-bit editions of Windows XP are limited to a total of 4gigabytes. Although the theoretical memory limit of a 64-bit computer is about 16exabytes (17.1 billion gigabytes), Windows XP Professional x64 Edition is limited to 128 GB of physical memory and 16terabytes ofvirtual memory.^[16]

Windows XP Professional x64 Edition also offers a number of benefits/advantages over the main 32-bit x86 versions of Windows XP:

• Supports up to two physicalCPUs (in separate physical sockets) and up to 64 logical processors^[17] (i.e.cores orthreads on a single CPU). Windows XP Professional for x86 supported up to two physical CPUs but is limited to a maximum of 32 logical processors.
• SupportsGPT-partitioned disks for datavolumes (but not bootable volumes) after SP1,^[18] which allows disks greater than 2 TB to be used as a single GPT partition for storing data.
• Allows for faster encoding of audio or video, higher video game performance and faster3D rendering than with 32-bit versions of Windows XP, in 64-bit optimized software.
• Immunity from certain types of viruses andmalware targeted at 32-bit versions of Windows XP, as most system files are 64-bit.

There are some limitations which apply to Windows XP Professional x64 Edition:

• Only 64-bit drivers are supported.^[19]
• Any 32-bitWindows Explorer shell extensions fail to work with the 64-bit version of Windows Explorer, however Windows XP x64 Edition also ships with a 32-bit version of Windows Explorer.^[20] It is possible to make this as the default Windows Shell.^[21]
• No native support forType 1 fonts.^{[citation needed]}
• IEEE 1394 (FireWire) audio is not supported.^[22]
• Hibernation is not supported if the RAM is greater than 4 GB.^[23] This would later be resolved byWindows 7.
• EFI and/orUEFI are not supported. A BIOS withAdvanced Configuration and Power Interface (ACPI) is required.
• OnlyEnglish orJapanese are provided as native display languages.Chinese,French,German,Italian,Japanese,Korean,Spanish andSwedish are available asMultilingual User Interface (MUI) packs for the English version.
• Additionally, the extra registers of the x86-64 architecture can cause a slight decrease in performance with certain applications compared to the same application compiled in 32-bit only x86 code running on 32-bit versions of Windows XP.

Windows XP Professional x64 Edition uses a technology namedWindows-on-Windows 64-bit (WoW64), which permits the execution of32-bit software. It was first used inWindows XP 64-bit Edition (forItanium architecture). Later, it was adopted for x64 editions of Windows XP and Windows Server 2003.

Since the x86-64 architecture includes hardware-level support for 32-bit instructions, WoW64 simply switches the process between 32- and 64-bit modes. As a result, x86-64 architecture microprocessors suffer no performance loss when executing 32-bit Windows applications. On the Itanium architecture, WoW64 was required to translate 32-bit x86 instructions into their 64-bit Itanium equivalents—which in some cases were implemented in quite different ways—so that the processor could execute them. All 32-bit processes are shown with *32 in the task manager, while 64-bit processes have no extra text present.

Although 32-bit applications can be run transparently, the mixing of the two types of code within the sameprocess is not allowed. A 64-bit program cannot use a 32-bitdynamic-link library (DLL) and similarly a 32-bit program cannot use a 64-bit DLL. This may lead to the need for library developers to provide both 32-bit and 64-bit binary versions of their libraries. Specifically, 32-bitshell extensions forWindows Explorer fail to work with 64-bit Windows Explorer. Windows XP x64 Edition ships with both 32-bit and 64-bit versions of Windows Explorer.^[20] The 32-bit version can become the default Windows Shell.^[24] Windows XP x64 Edition also includes both 32-bit and 64-bit versions ofInternet Explorer 6, so that users can still usebrowser extensions orActiveX controls that are not available in 64-bit versions.

Only 64-bit drivers are supported in Windows XP x64 Edition, but 32-bitcodecs are supported as long as themedia player that uses them is 32-bit.^[19]

By default, 64-bit (x86-64) Windows programs are installed onto their own folders underC:\Program Files, while 32-bit (x86/IA-32) Windows programs are installed onto their own folders underC:\Program Files (x86).

A few features that were included with Windows XP were dropped from Windows XP Professional x64 Edition. Most were dropped as a result of x64 Edition being based on the Windows Server 2003 codebase. Another result of this is the popular registry hack that enabled Windows Update to think your Windows XP system isWindows Embedded POSReady 2009 did not work on Windows XP Professional x64 Edition. A workaround does exist although it is a slow manual process that involved manually downloading each update and modifying the files.^[25][26][27]

• NTVDM andWindows on Windows (not to be confused with WoW64, which was new in this edition of Windows) were removed, so16-bit Windows applications or nativeMS-DOS applications cannot run.^[28] A similar case happened with both versions ofWindows XP 64-bit Edition forItanium. Some old 32-bit programs use 16-bit installers which do not run; however, replacements for 16-bit installers such as ACME Setup versions 2.6, 3.0, 3.01, 3.1 andInstallShield 5.x are hardcoded intoWoW64 to mitigate this issue. This is true for later 64-bit versions of Windows.^[19]
• COMMAND.COM, which is a command interpreter exclusive toMS-DOS andWindows 9x, is no longer included.
• Program Manager was removed and replaced with Windows Explorer. The executable is still present, but it was replaced with acompatibility stub that redirects to Explorer. The executable itself would not be removed entirely untilWindows Vista.^{[citation needed]}
• Win32 console programs (includingCommand Prompt) have no full-screen mode. This also applies to later versions of Windows.^{[citation needed]}
• Media Bar, which replaced theRadio Toolbar inInternet Explorer 6,^[29] was removed.^[30]
• The Web Extender Client component for Web Folders (WebDAV) was not included.^[31]
• Spell checking inOutlook Express was removed.^[32]

The RTM version of Windows XP Professional x64 Edition was built from the Windows Server 2003 Service Pack 1 codebase.^[4][33][34] Because Windows XP Professional x64 Edition comes from a different codebase than 32-bit Windows XP, its service packs are also developed separately.^[35] For the same reason, Service Pack 2 for Windows XP x64 Edition, released on March 13, 2007, is not the same as Service Pack 2 for 32-bit versions of Windows XP.^[35] In fact, due to the earlier release date of the 32-bit version, many of the key features introduced by Service Pack 2 for 32-bit (x86) editions of Windows XP were already present in the RTM version of its x64 counterpart.^[4] Service Pack 2 is the last released service pack for Windows XP Professional x64 Edition.

A machine running Windows XP Professional x64 Edition cannot be directly upgraded to Windows Vista because the 64-bit Vista DVD mistakenly recognizes XP x64 as a 32-bit system. Windows XP x64 does qualify the customer to use an upgrade copy of Windows Vista or Windows 7, however it must be installed as a clean install. Despite this, there is a workaround available via third-party tools, including MSXML 6 and .NET Framework 2 as requirements, that makes upgrading from XP x64 to Windows Vista possible.^[36]

The last version ofMicrosoft Office to be officially compatible with Windows XP Professional x64 Edition isOffice 2007, howeverOffice 2010 can be unofficially installed by disguising the Windows version using Application Verifier. The last version ofInternet Explorer compatible with Windows XP Professional x64 Edition isInternet Explorer 8 (Service Pack 2 is required).

Windows XP Professional x64 Edition follows the same support lifecycles as with all other versions of Windows XP. On April 14, 2009, Windows XP Professional x64 Edition's mainstream support expired and the extended support phase began. During the extended support phase, Microsoft continued to provide security updates; however, free technical support, warranty claims, and design changes are no longer being offered.^[37] Extended support lasted until April 8, 2014, in line with all other Windows XP editions.^[37] After this date, no more security patches or support information are offered.

Although Windows XP Professional x64 Edition is unsupported, Microsoft released an emergency security patch in May 2017 for the OS as well as other unsupported versions of Windows (includingWindows Server 2003,Windows Vista andWindows 7 RTM without a service pack), to address a vulnerability that was being leveraged by theWannaCry ransomware attack.^[38][39] In May 2019, an emergency patch was released to address acritical code execution vulnerability inRemote Desktop Services which can be exploited in a similar way as the WannaCry vulnerability.^[40][41]

Microsoft announced in July 2019 that the Microsoft Internet Games services on Windows XP and Windows Me would end on July 31, 2019 (and for Windows 7 on January 22, 2020).^[42] Others, such asSteam, had done the same, ending support for Windows XP and Windows Vista in January 2019.^[43]

In 2020, Microsoft announced that it would disable the Windows Update service for SHA-1 endpoints for older Windows versions. Since Windows XP Professional x64 Edition did not get an update for SHA-2, Windows Update Services are no longer available on the OS as of late July 2020.^[44] As of March 2024, many of the old updates for Windows XP Professional x64 Edition are available on theMicrosoft Update Catalog.^[45] A third-party tool named Legacy Update allows previously released updates for Windows XP Professional x64 Edition to be installed from the Update Catalog.^[46]

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