Microsoft offer the Internet Explorer 7 Blocker Toolkit to disable automatic delivery of Internet Explorer 7 as a high-priority update via Automatic Updates and the Windows Update and Microsoft Update sites.
http://www.microsoft.com/downloads/details.aspx?familyid=4516A6F7-5D44-482B-9DBD-869B4A90159C&displaylang=en
Supported Operating Systems:
Windows Server 2003 Service Pack 1
Windows XP Service Pack 2