The Microsoft Download Center page, Toolkit to Temporarily Block Delivery of Windows Server 2003 Service Pack 1, contains the following description:

"While recognizing the security benefits of Windows Server 2003 Service Pack 1 (SP1), some organizations have requested the ability to temporarily disable the automatic delivery of this update through Automatic Updates (AU) and Windows Update (WU)."

You can download the toolkit from

The mechanism that temporarily disables delivery of Windows Server 2003 SP1 will be available until March 30, 2006.