Computer BSOD

Hey i have a.

Intel Core 2 Quad Q8200
MSI Ms-7510 Mother Board
DDR2 2048, 800- Upgrading to DDR2 8gigs of 1066 next week
Windows Vista Home premium 64bit
Zotac GTX 285
X-Fi Xtreme Audio
500gig Sata
650w eXtreme power duo, Cooler Master
Antec 900 Case
GeminII Cpu cooler with 2 120mm blue led silent fan by coolermaster

Video card temp at idle GPU-32 at 61% fan speed- program EVGA precision
648 core clock
1475 Shader Clock
Memory Clock 1242
No over clocking done.

Problem, everytime i play S.T.A.L.K.E.R Clear skys for about 10 mins, i get BSOD also the same on Crysis Wars and warhead not the exact same time thoe. Already tested HDD for bad sectors but its 100% in perfect condition even thoe loading up crysis makes it squeel and also on stalker loadup. now for ram i had 3 gigs but when problem accured 3rd time today my friend said to me it is RMA ram so i took it out and problem persisted, now i playing both games MAXXED out DX10 shadow effects EVERYthing as possible high as it goes, STALKER i get 21-45 or more fps but i keep blue screening im starting to think its the RAM to small for video card, or my motherboard MS 7510 is starting to fail me, i have checked all drivers and everything is uptodate. if anyone has any infomation that can help me out plz help lol, i want to play my games also B4 i updated Stalker so that it has Dx10 shadow it dint BSOD on me. thanks Shanden