I am computer tech, solve this kind of probs all the time.
But this problem has gone for about a year now:
45 PCs, all IDENTICAL hardware -P4,128ddr- & software -win98- (its a school)
Supposedly (never seen it) PC freezes & video on monitor becomes corrupt, turns into this multi-colored pattern of flashing tiny squares.
I am not absolutely sure if background is completely black or if it remains last thing on desktop.
This is what Ive tried:
1. Updated drivers
2. Changed settings on bios, mainly shared memory resources, irq assings for vga, etc.
3. Checked for overheating , installed extra fans.
4. No electrical probs.
5. Changed motherboard (on 1 pc). Of course diff. vendor.
Oh, PC can freeze just about anytime, for no particular reason whatsoever. Reboot and all is ok, same PC will not necesarily fail again, at least not in the same day, week or month.
2 PCs can fail at the same time (or not) and maybe none will fail in a week or 2.
See why I am going nuts? If you have any ideas or want more info please ask.