Wow, I think we have similar systems! I've got an ASUS A7N8X, AMD 2100+, and ATI AIW 9700 running XP SP2. Given that this never happened once on Win2K, and started shortly after I installed XP, this also sounds like a possible cause. I've already updated my BIOS for something else, so I have the latest version of that. I'll try downloading the actual ATI drivers soon.

What's frustrating is that this error is completely at random. A couple days ago, it happened about 30 minutes after I booted my PC. At this moment, the machine has been on for a couple days with no problems. I've started feeling a little anxious when using my home PC, and that's not very fun...