|Does it have anything to do with NT AUTHORITY\SYSTEM. It is possible that you have a computer that hasn't been updated/turned on for awhile and actually has the old Blaster worm or something similar.|
If that is the case, download Service Pack 3 network installation from Microsoft and burn it on a cd.
Boot up the infected computer and press F8 as it starts (right after BIOS screen or computer logo) and install SP3 in safe mode. If it is one of the older worms that caused that issue the service pack should eliminate your problem.