Try clearing the CMOS, the location can be found at the motherboard manual, u can try removing and cleaning all memory cards and anything that can be pluged in.

If anything works try testing each part os the PC, remove 1 memory and put it on other pc to see if its working and do this with all the cards.

Theres no way to certainlly say whats going on so you have to test everything, Hope it helped good luck

You should overclock your GPU by 10 - 10 MHZ or less and keep checking its temperature and making stress tests at each overclock you make,btw and make sure you have a good cooling system.

If you push too hard without checking the conditions of the GPU u can get it burned so be careful

Im a Vista Ultimate user and most of the games I have works fine on it but Vista games are slower than Windows Xp games.