Computer likes to reboot -- directx? drivers?

[Peegee]

The computer's randomly rebooting again. This time the specs are as follows:

- Desktop PC
- some Radeon 9200 card
- random asus mobo/ P4 2.8 chip
- 2x 3200 ddr 512 ram
- 1x 2700 ddr 512 ram
- 3 fans powered by IDE, one by mobo (or it would give me a cpu fan not working error)
- 400W PSU

Anyway everything is as it was -- same windows install from before I went to HK. However I couldn't install directX -- it apparently was installed already. In any case, when I run directX related screen savers (like 3D text) or play video games requiring directX (like doom3 or world of warcraft), I will randomly get one of the following:

- computer freezes
- hard reboot
- drawing errors leading to freezing

Never an error -- just plain freezing.

Now is this a driver error? I installed the drivers from the cd that came with the card, plus windows updates. I *am* planning on getting a new video card (upgrading from 128 to 256), but like the dvd burner and etc, if it can wait, it can wait.

So what think you? hardware/software? It's not a virus. :D