Severe Hang Problem

I recently upgraded my computer. Right away, when I started playing 3d
games, the system completely locked, forcing me to restart. This happens
without fail, every time, often within 10 minutes. This didn't happen
before. My current configuration is:



*denotes new parts



*AMD Athlon 3200+ 2.2ghz

*512MB DDR-SDRAM (Corsair Value)

Rosewill Radeon 9600 256mb (Catalyst 4.12)

Windows 2000 Professional SP4

*ASUS A7V600-X

*VIA KT600 Northbridge

300W Power Supply

BIOS Rev. 1006



Every once in a while a given game will last 2-3 hours. However, on
occasion, the computer will freeze while in Windows, and NOT in a game.



I've upgraded everything under the sun. I've changed the AGP settings
and even turned it off, along with the VPU recover, but to no avail.
What is my problem here and how do I solve it in an inexpensive way?

--
if all else fails: go fsck yourself!

the email address is not real (leading numbers are an obvious
indication) to get the real address, take each individual part
and flip it around so would be