One other thing for you to check - the power supply to your PC (not the PSU inside of it). That is a powerful PC, and it will be drawing a lot of current from the mains.
If you have it plugged into a cheap power adaptor for example, that could easily cause the problems you've got. I had exactly the same issue as you, my PC would reset itself for no reason at all - it didn't matter what I was doing, sometimes after 20 mins, sometimes 2 days. It got VERY annoying. A mate of mine is an electrician and he tested the socket and found that the occassional small peak and drop in power was causing the PC to reset itself.
I bought an APC EPS800 UPS system, which is like a large 4-way mains apator with 15min battery back-up built in, and it has been utterly perfect ever since! The UPS regulates the power draw, keeps the signal clean and tidy.
Definitely have a look in this area if your BIOS change doesn't fix it.
Heavy on the Magick