Totally Screwed. Need any help I can get.

[OmnipotentKiwi]

Alright guys, normally I don't ask for help but this problem has me totally confused w/o anymore ideas, so:

Symptoms:
Random Program crashes: Various programs will become non-responsive and close for no apparent reason.
High Load Tolerance: When any kind of high load occurs, the computer restarts itself.
Shut Down/Restart: Whenever shutting down or restarting, the computer will often hang indefinitely, even though not being fully "crashed" (num/caps lock still works, so the keyboard is still responsive).

Things I have tried:
Full format. My initial diagnostic was that a Planetside crash totally screwed Windows since a lot of the clues pointed in that direction. restore did no good either. The full format did improve the condition, but I doubt it was connected in anyway.

Full Virus Scan: Updated Norton, nothing found.

Individual removal, cleaning, and reinstallation of all hardware: I cleaned my vid card/ram/PCI slots, etc w/ contact cleaner w/ the power off after waiting a while to prevent damage. Reinstalled all the parts, and still nothing.

Recent changes to my computer:
The only serious change in the apst three months was a very recent RAM upgrade. Even after removing the new stick of RAM, the problems still occur.

Comp Specs:
Gigabyte Intel 845G Mobo
P4 2.20Ghz
Mushkin Black PC2700 DDR CAS222. 2 sticks of 512MB
Western Digital "J" HD. 120GB w/ 7200RM
Audigy Platinum
OS: XP Pro

So, please help if you can.