SVCHOST.EXE or Windows Update pegs your CPU at 100 percent usage fix - formerly PSS-only hotfix is now a public download for XP and 2003

I've only seen this happen on a few virtual machines from time to time without a concrete cause why one VM would do this and another would not. I've also seen it on one laptop, but it looks like the problem is pretty widespread overall. It would typically happen when Windows Updates were applying or scanning.

You can download the XP hotfix here and the 2003 hotfix here.