Random Rebooting

I’m debugging a machine that is currently running an AMD K6 400mhz processor, 256k ram, 8m video card, sound blaster sound, …., and win98. THe problem is that this machine randomly re-boots and then performs scandisk before being usable again(major downtime). The only thing that seems consistant is video intensive games, Winamp, and most audio cd software titles will cause the reboot every time. I guess I’m looking for some way(diagnotic tool, trick, or just plain ol’ magic) that will helpme debug this a little better before I resort to replacing cards one at a time. All comments and suggestions are welcomed.