Windows x64 vs. windows x86

XP x86 is 5.1 kernel

XP x64 is 5.2 kernel (same like Win2003 Server)
XP x64's SP2 (12. March 2007) is much much newer than XP x86's SP2 (9. August 2004)

x64 edition of windows xp has the codebase of the windows 2003 server platform and not the windows xp client platform.
For windows xp x64 (amd64/emt64) you need to get the windows 2003 servicepacks (for x64 ofcourse).
It has nothing to do with the normal 32bit platform of windows xp home/professional/mediacenter/tabletpc.

Download of windows XP x64 (deutsch)

Download 2 (corporate edition)

windows XP SP3 RTM standalone

Service Pack 3 Info:

As per the unofficial timeline, Windows XP Service Pack 3 (SP3) has been uploaded to Microsoft's servers. Currently, the final build is only available on the download.windowsupdate domain in the following languages: Chinese (Hong Kong), Czech, English, French, German (Deutsch), Hebrew, Japanese, Polish, Russian, Simplified (Chinese), Spanish, and Traditional Chinese. According to Microsoft TechNet, the 300MB+ x86 standalone installer (build 5512) will not be available today on the Microsoft Download Center nor on Windows Update.

There will be no x64 version of SP3 released; Windows XP x64 will be updated at the same time Windows Server 2003 is updated, since it is derived from the codebase of the latter. Although Microsoft has still to confirm the date, SP3 should be rolled out via Automatic Updates on June 10, 2008.

The service pack contains all previously-released Windows XP updates, including security updates, out-of-band releases, and hotfixes released since Windows XP SP2 hit Microsoft's servers back in August 2004. There are reportedly 1,073 fixes in SP3, as well as various performance improvements. Every service pack Microsoft releases is cumulative, meaning it is possible to install (or slipstream) SP3 onto Windows XP SP1/SP2. Windows Internet Explorer 7 is not included as part of SP3 and still must be downloaded and installed separately (unless it is already installed).

With SP3, Microsoft has back-ported four Vista features to XP, including Network Access Protection (NAP) in order "to help organizations that use Windows XP to take advantage of new features in the Windows Server 2008 operating system." The four features that are no longer Vista-specific are as follows:

• NAP is a policy enforcement platform meant for enterprise use that blocks systems attempting to access a network until they meet whatever security criteria the corporation has in place.
• "Black Hole" Router Detection helps detect and protect end users from a router that drops packets without returning the specified Internet Control Message Protocol response.
• Microsoft Kernel Cryptographic Module incorporates cryptographic algorithms in a single module other kernel mode drivers are capable of hooking into and accessing.
• The new Product Activation module allows users to install XP without entering a product key at installation.

Just over a month after the release of Vista SP1, XP SP3 hit RTM on April 21, 2008, as the rumors predicted. Up until then, Microsoft continued to stubbornly say that SP3 would go final in the "first half of 2008." The last beta build Microsoft released to the public was XP SP3 RC2 Refresh, available in English, German, and Japanese.

MSDN and TechNet subscribers received the final English 544.86MB ISO image a few days ago. As with Vista SP1, however, subscribers had to fight to get the final build before it hit RTW. MSDN and TechNet subscribers were supposed to get SP3 on May 2, 2008, or three days after it was available publicly.

With the release of SP3, XP will be found on consumers' PCs for years and years to come. On the other hand, with Windows 7 a couple of years out, and with the recent broad release of Vista SP1, Windows XP's life as market leader is slowly coming to an end.

The keyword here is "slowly." Microsoft has extended the life of XP Home until at least June 2010 for budget laptops, and even Apple is supporting XP SP3. Furthermore, although Microsoft has plans to stop selling XP to most manufacturers and system builders on June 30, 2008, OEMs are fighting back. 

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