In an announcement posted on Microsoft TechNet, Chris Keroack, Release Manager, Windows XP Service Pack 3, said that the next big update of Microsoft’s Windows XP is ready for release to the web.

“We are also in the final stages of preparing for release to the web (i.e. you!) on April 29th, via Windows Update and the Microsoft Download Center. Online documentation for Windows XP SP3, such as Microsoft Knowledge Base articles and the Microsoft TechNet Windows XP TechCenter, will be updated the,” wrote Keroack. The new service pack will be available as an Automatic Update during this summer, he added.

Windows XP Service Pack 3 (SP3) includes previously released Windows XP updates, including security updates and hotfixes. It also includes select out-of-band releases, and a small number of new enhancements, which do not significantly change customers’ experience with the operating system.

Microsoft is not adding significant Windows Vista functionality to Windows XP through SP3. However, SP3 does include Network Access Protection (NAP) to help organizations to work with the new features of the Windows Server 2008 operating system.

NAP is a policy enforcement platform built into Windows Vista, Windows Server 2008, and with which a user can better protect network assets by enforcing compliance with system health requirements. Using NAP, the users can create customized health policies to validate computer health before allowing access or communication and automatically update compliant computers to ensure ongoing compliance.

Besides NAP, Windows XP Service Pack 3 will include Management Console 3.0, which appears in Windows Server 2008 and Vista and the new Windows Installer 3.1.

According to Microsoft, Windows XP SP3 will be available via Windows Update as a 70MB download or as a full installation weighing in at 580MB at Microsoft Download Center. Windpws XP SP3 is cumulative, so users can install SP3 on top of Windows XP SP1 or SP2 and supports the same languages as Windows XP did in its initial release.