Originally Posted by grey_1
I would try stressing the cpu and mobo at default speeds. If it acts up you may have a faulty mobo or flakey bios.
I still have XP pro running on 4Gb ram and it over clocked pretty decent, except I have 2x2Gb. I hear 4x1Gb sticks can be hard on overclocking..maybe try with only 2Gb? That could be your issue.
What program would be good for stress testing?