My new desktop PC keeps stuttering!?

I tried overclocking it a tiny bit, from 2GHz the highest stable frequency was 2.18, so not too much of an overclock.

The other day, i tried a 2.2 (wanting to do it in increments as suggested) & the mobo's OC/overheat/dunno safety mechanism kicked in & the comp switched off. It failed to load past the BIOS welcome screen a couple of times (not even letting me enter setup); before finally getting into the setup & resetting everything.

Now when i load up, everything's fine except everything has a stutter, mostly in games. No loss of performance at all, but just has this frequent "skip". it's most noticeable in games & audio.

specs:

Mobo.: ASUS A5VD2-VM

CPU: Intel E2180

RAM: 2GHz 667MHz

GPU: GeForce 9600 GT

HDD: 250GB SATA II

PSU: Unsure, its 500W. (heard PSUs can cause this?)

I'm guessing those're all the specs needed. Have been using PCs for ages like a maniac so i can hopefully take on board all suggestions. have searched many possibilities; keen on BIOS update but no floppy yet