There's your problem right there :P Naw, I'm kidding.
Have you cocked up an install? Enter safe mode and check what stuff is running. Specifically, head to regedit (start > run > regedit) and look for:
HKEY_* > Software > Microsoft > Windows > CurrentVersion > Run/RunOnce/RunService
It'll more than likely be there. If possible, go to add/remove programs and see if there's anything there that you don't need.
It all boils down to corruption of some kind, and the only option is to stop it running when the PC boots or to get rid of it.
I seriously can't see this being a malware problem either, but it's always possible.