Weird problem with XP Pro

When I raise my VCore higher than 1.7v in XP Pro, my computer reboots randomly with no error messages. The higher the VCore, the faster the computer reboots. I know for a fact it's not a hardware problem because I ran tests and replaced everything. Could it be my XP1800? I get no reboots in Win98SE even at 2.1v.

A shot in the dark; does raising your core voltage cause your +5 volt to drop? What does it run before and after?

yeah, from 4.92 to 4.88 but the psu is an Antec 430w. I've tried another Antec 430w and still got the same problem.