Probably Win 2000? I would go with just reformatting the bastard. You can keep your files and such like. It would check whether it is a Virus or a Motherboard Problem. Or RAM - a lot is being done while Booting up so maybe its not stable enough or too old to do it anymore.
A Knight is sworn to Honour. His heart knows only Virtue. His blade defends the helpless. His might upholds the Weak. His word speaks only truth. His wrath undoes the Wicked.