Derek was on a file sharing site, he downloaded a file, and the next day his computer was unusable. It just would boot up to a random pattern. Leo says that often, malware is distributed via filesharing sites. So it may be malware. Malware would typically lock the user out and then try to extort money to unlock it. This isn't what it's doing, though.
Leo suggests scanning the drive from another computer to see if it detects something. It could be a problem with the video card, or the drivers are corrupted. Rebooting into safe mode could indicate whether or not the drivers are bad. Reinstalling Windows is almost always the best way to remove malware, though.
Try a boot CD and if there's no problems, then he'll know his operating system has an issue. If he has problems on the boot CD, then it's a hardware problem. Then he should replace the video card.