Windows XP build 2600.5512

Windows XP build 2600.5512 is the official RTM build of Windows XP Service Pack 3. It was released to manufacturing on 21 April 2008 and was made available for download via Windows Update and the Microsoft Download Center on 6 May 2008. It was also automatically distributed to consumers running Windows XP through Automatic Updates on 10 July 2008.

This release would be used as the base for Windows Embedded Standard 2009 and POSReady 2009. It was also pushed out to Windows XP Starter Edition, Windows XP Tablet PC Edition 2005, Windows XP Media Center Edition 2005, Windows Fundamentals for Legacy PCs, and Windows Embedded for POS. It is the last version to support upgrade paths from Windows 2000.

== Changes from Windows XP SP2 ==
 * Users can now complete OS installation without providing a product key and the OS will instead prompt the user for a product key later to complete activation.
 * Includes 9 features by default that were already available in previous updates such as MMC 3.0, MSXML6, Windows Installer 3.1 v2, Background Intelligent Transfer Service 2.5, IPSec Simple Policy Update, Digital Identity Management Service, Peer Name Resolution Protocol 2.1, Remote Desktop Protocol 6.1 and WPA2.
 * Improvements to Black Hole Router Detection.
 * Windows Script Host has been updated to version 5.7.
 * Adds support for Network Access Protection (NAP) which was backported from Windows Vista and Windows Server 2008.
 * Adds support for CredSSP Security Service Provider.
 * Adds Descriptive Security Options User Interface to the Security Options Control Panel applet to provide more information on Security settings.
 * Enhances security for Administrator and Service policy entries.
 * Microsoft Cryptographic Module adds support for SHA2 hashing algorithms.

Visual styles
In the Japanese version, If Luna theme was used on the first boot and changed to the Windows Classic style in the appearance tab from the Display Control Panel applet, it oddly enables the Blue Luna theme on the next reboot.