xp restarts at random

ok, for almost a month now i have been trying to get my computer to stop crashing, and im down to 3 things...the mobo, the chip, or my case(lol). I used to have 2 sticks of 2700, a ti4200, 160gb westerndigital, a cheap 400w powersupply. I have the k8t Neo(non-platnium), and a AMD64 3000+. I still have the same board, chip and harddrive, but i formatted and installed xp pro, put in a new 512 stick of 3200, a new power supply, and a 9700 pro. For a while i was getting physical mem dumps about every 5 min, now it just restarts, sometimes 5 min, sometimes after an hour. I have just formatted so i don't think its virus related, and i know the vid card is good. Now when i open halflife(through steam) my monitor goes out and says out of frequency. This also puzzles me because i was playing dod last night for about an hour, i turn it on this morning and boom, a new problem to confuse me. The power supply im useing is not BRAND new but it is fairly new. One of my friends said it could be the voltage coming into my wall outlet, but i doubt that too. Any help is appreciated. ~kurt~

win xp pro
radeon 9700 pro
msi k8t neo
amd 64 3000+
512(1)corsiar value select 3200
350W power supply
160Gb wester digital (7200rpm,8Mb buff)
(bios and chipset have been updated this week)

(^^;?(I couldn't make out the whole story.)

In any ways,

From property of MyComputer > advanced > settings > restart and recovery

Uncheck "Automatically Restart" (You'll see blue screen instead.)

Check in bios, Memory / Voltage setting

Clock down CPU.

Run Memtest from floppy.

Introduce Hardware Monitor.

Thread moved.

EDIT: And please don't cross post questions.