As it did previously with Windows XP Service Pack 2 (SP2), Microsoft will make available a tool to block the automatic deployment of Windows Server 2003 Service Pack 1 (SP1) via Automatic Updates (AU). The blocker tool will give system administrators that aren't ready to deploy Windows Server 2003 SP1 more time to prepare.

"This mechanism blocks the download of Windows Server 2003 SP1 via AU while allowing AU to download all other security updates," a Microsoft representative told me. "This mechanism affords systems administrators additional time to put in place a patch management solution outside of AU. Most enterprises manage updates via \[Systems Management Server\] and Windows Server Update Services, so this affects only a handful of enterprise customers."

Windows Server 2003 SP1 first shipped in late March, and it has been deployed to at least 2 million servers worldwide so far. Microsoft says that the blocking tool will be in effect until March 30, 2006, or about one year after the release of Windows Server 2003 SP1. For more information and the free download, please visit the Microsoft Web site.
http://www.microsoft.com/downloads/details.aspx?familyid=FC145B0B-C148-445A-82BA-9B2F3AEF6E60&displaylang=en