Could be memory problems, could be overheating problems, could be driver problems, could be many things.

Try running your computer with the side panel open to allow good airflow and see if the BSODs continue.

Run <a href="http://www.memtest86.com/">this</a> to check for faulty RAM.

Scan your computer for viruses and spyware.

If all else fails, reformat. Finding troublesome drivers is a big hassle. Your best bet is to reformat and install drivers one by one and see if they cause problems. Oh, and don't bother with SP2 if you're coming from a non SP Windows install as it'll just bloat your system. Stick with SP1.