Roseman wrote in to let us know that the Windows Service Pack blocker tool can now block the following service packs from installation:

• Windows Server 2003 Service Pack 2 (valid through March, 2008)
• Windows XP Service Pack 3 (valid for 12 months following general availability)
• Windows Vista Service Pack 1 (valid for 12 months following general availability) 

So, if you want to prevent your machines from automatic updates (provided you don't use WSUS), you can download this handy tool from http://www.microsoft.com/downloads/details.aspx?FamilyID=d7c9a07a-5267-4bd6-87d0-e2a72099edb7&DisplayLang=en