My computer has a mind of its own - Strange problem

[FollowThisLogic]

If you were successfully running XP home, it shouldn't be a bios issue, or anything so complicated.

Why not? XP Home, just like XP Pro, is based on NT. Completely different from the 9x series. It's also four years newer - they may have yanked some legacy BIOS functionality that 98 still had in it, perhaps in order for it to work better with newer computers. If it can't shut itself down, and instead she must shut down manually, it stands to reason that Windows cannot properly deal with the advanced power management, right? And wouldn't that be a function of the motherboard, and hence, the BIOS?

Anyway, whether it does the trick or not, a BIOS update isn't a bad idea. And it isn't very tough to do.