Comp feezes when running games

Hi

recently my power adapter died. i replaced it (together with a new box and more ventilators) and apparently everything works excpet that when I run games (even games that worked perfectly before the incident), computer freezes completely with a hissing noise coming out of the speakers. I have tried changing some of the settings, both in the sound card and in the graphics card, and still no luck. the freez ups occur randomly, sometimes right after starting the game, other times much later.

Any idea what could be damaged? Could this be a problem due to the fact that I installed the latest directX 9.0a?

I tested my RAM and apparently it is fine.

Here are the specs of my computer:

- MB is ABIT BD7, ID=i845-W83627HF-6A69VA1DC-6H
- P4 1.8 GHZ
- 2 DDR RAM, 1 of 256 , 1 of 512
- Gaphics Card is Visiontek Xtasy with Nvidia GeForce MX 400
- Sound Cards is Sound Blaster Audigy

- Running Windows XP Home Edition

- All latest drivers and Windows Updates installed


Any help would be appreciated - thanks!