Computer Freezes, and i cant figure out why?

every time I start a game, or just simply scrolling the mouse, the computer seems to just freeze at its own will, i may not even be doing anything and it will stall or freeze. Sometimes it will freeze and without a reboot, if i just let it sit it will begin working again, anywhere from 10min-1hr later, almost like it was lagging.

Technology:
2.83 GHz Intel quad2 core proc Q9550
Core-45nm
L2 cache-12 MB

32bit Windows Vista home premium
4 gigs of Ram (will be running 8gig with 64 bit windows when it arrives in mail)

1000 w power supply
10000rpm 150 GB HD- boot HD
7200 rpm 320 GB Storage HD
Extreme Striker 2 motherboard=- no overclocking at the moment, with added hd sound card
evga GeForce GTX 260 superclocked edition 826MB DDR3 graphics card

what can i do, or does anyone have the same problem, i have inserted ram into slots 1 and 2 on motherboard, and i am unsure on how to properly check to see if they are operating right, Please help