After removing XP Security Center 2012 fake anti-virus from a computer, I found that automatic updates was no longer running. Upon trying to get them to run, I found the service didn’t even exist!
Well, it turns out if you have a copy of your Windows disc, it is a fairly easy fix.
%windir%\System32\rundll32.exe setupapi,InstallHinfSection DefaultInstall 132 %windir%\inf\au.inf
And it will likely ask you for your operating system CD. You may be able to give it a local path, but in my case I had to point it to the network installation source.
Thanks to Microsoft for putting together a good KB on restoring automatic updates service.