I've got a slight update here. I've managed to get the system pretty stable in Vista's Safe Mode, and Ubuntu seems relatively stable. However, when I boot into Vista normally, I always blue screen. Sometimes immediately, sometimes in 5 or 10 minutes. Normally this would point to a software issue. Multiple re-installs, both fresh, and from backups don't fix the problem. So, that leaves it at a hardware issue. What hardware isn't being used in Safe Mode or Ubuntu? I suspected the sound card, removed it, and uninstalled drivers, no luck. Video cards, no luck. I guess I'll try USB devices next, but geez, what a pain this thing is being...