I have been having issues for quite a long time with my system crashing.
When I originally had the issue I did the following.
1. have 2 gfx cards, so tried removing each one and running on 1 card for a while
2. bought a psu tester, which showed my psu was fine
3. tried removing RAM sticks
no.3 seemed to solve the issue, with 2 of the sticks removed, I didn't have any crashes for a while, so I got them replaced and didn't have any issues for a few months.
But now the crashing has returned.
I have run the windows memory test and that passes, so I left memtest running over the weekend, and that crashed. So not sure if this means there is memory issue or not.
have you tried cleaning all your fans(CPU, graphics card, and Power Supply) in your PC...people overlooked this assuming computers themselves. Try air-in-a-can and blow out the fans. Next, defrag, clean your registry and history. Crashes don't always come from hardware, it might be something you're not doing or not compatible to your PC.
vacuums create static electricity. I would use cotton swabs and canned air.
the older 775 motherboards used ( i think ) 2.0/2.2 volt memory sticks. And I think I remember when populating all 4 slots I had to slightly bump the voltage just a tiny hair. Have you tried nudging it a little ?