Windows Server 2003 SP1 Automatic Updates Blocker
Like XPSP2 before it, Windows Server 2003 Service Pack 1 is going to be distributed via Automatic Updates.
The start date for automatic updates is July 26, 2005.
If you'd rather move at your own pace over the next year, you'll want to look at the Blocking Toolkit, and the following information:
https://www.microsoft.com/WindowsServer2003/evaluation/news/bulletins/ws03sp1blockertool.mspx
FAQ: https://www.microsoft.com/windowsserver2003/evaluation/news/bulletins/ws03sp1blockertoolfaq.mspx
The blocking mechanism expires on March 30, 2006.