If you have a xp disk you can try automated system recovery
(Boot from xp disk and after you press F8 and it finds an installation of XP it will ask you if you want to attempt recovery)
Then boot safe mode and run malwarebytes.
After a virus scan in safe mode always run again in normal mode.
You could also try something like the ultimate book disk for windows
With this you can boot a "mini" XP and check for virus.