What kind of powersupply do you have and how old is it? Check the molex connections to ensure that they're all seated properly. As a matter of fact, check all your components to ensure that they're making good contact. Reseat your RAM, CPU, video card, heatsink(s), and power connectors. I often see powersupplys being at fault for random reboots, because most motherboards will automatically shutdown and restart if they detect a brown out or spike. If you've reformatted and reinstalled Windows, guess what??? Doing it 2 more times wont change anything. I suspect a hardware problem for your freezes and random reboots. As for the video card, chck your manufacturer's website to ensure you have the latest driver updates.