Hardware Troubleshoot / System Freeze

[Lennox1980]

I'm hoping some of you may be able to help with a hardware issue i'm having. I just moved into a house and started having lockup/freeze problems with my pc.

-software is fine, no virus or anything, i keep it clean.

lockup/freeze happens:

-when system is idle (over night or just 30mins)(multiple times)
-on restart (at the windowsxp load screen)(multiple times)
-last night i exited bf2 and it locks (no prob with wow tho)
-when i ran avg anti virus it gets to/just passed the registry check and freezes
-after a reboot i accessed my 2nd (older) storage drive and it froze

** everytime it freezes, there is a click just as it happens. i'm thinkin one of my drives (new 80g wd or older samsung? 120g)

i do have a surge protector.
my psu is generic with the case (430w)
voltage in the bios looks fairly normal

im thinking hdd or psu, maybe ram, maybe surge protector? man, i dont know. i just don't want to replace part after part to find the problem. should i volt test something? OR is there any test i can run to see im one of my drives are shot? HeLP?

thx