OK, you seem to have eliminated the malware possibility.

The next thing that I would try is to go to the ATI site and get the latest drivers for your Radeon. Uninstall the old drivers first. I once had a Radeon that was only 12 weeks old (from being manufactured!) I had problems and found that there were new drivers only one week old that fixed them.

My experience with video cards is that it is usually the drivers or overheating.

Are you overclocking the video card? My advice is to start with the standard settings until you are certain that you have a stable system.

My thinking is that once your PC has booted up, then your BIOS has done its job, and should not have any more influence on that session?

Good luck