Asus P5nt-WS Unstable

My Pc Specs are

Mobo: Asus P5nt-ws (680iLt Sli)
Cpu : Q6600 3.15Ghz Nb-1.4V
Ram : 2*2 Gb Transcend 800Mhz
Gpu : XFX 8800gt And Palit 8800Gt in Sli
Hdd : 2 * 80Gb Raid(0), 2* 250Gb Raid(0) , 1Tb (Data)
Psu :Tagan Bz series 800W Psu

Now my problem started like this i was running stable at 3.0Ghz with 1*8800gt I went ahead and bought another one(XFX) Bought the 800W Psu due to the load increase.

After enabling Sli first the system would start artifacting within 2-3 mins from start in Crysis. then somehow after swapping the cards up and down and inserting Xfx card in master and Palit in Slave and trying different sets of drivers i managed to make it work stably but not for long 2 weeks later my system would lock-up and give BSod's upon start i thought a problrm with the Ram and got a replacement still the problem won't go away. i got two 1gb sticks of ram from my friend and put it in my system and the problem went away now as soon as i put one of my old sticks it would again start behaving the same so i went and bought a third stick of the same model Corsair valueram and put three of them together again the same BSOd's and lockup's so i came to the conclusion that my system is not supporting more than 2gb of ram sticks now after 2weeks of fighting with the system i removed the second Vga card and booted the system with my old 2*2gb sticks just to check and behold it was working fine again but as soon as i plug the Vga back in it will again Lockup. But now even with 2gb corsair it is Locking up again the same way it used to do before. i finally have removed the second Video card and kept it on my desk the system is now running Stable. But i need the second card to work that's what i bought it for can someone Help me figure out the problem. I am totally fed up now.
Thanx for help in advance.

Sorry Got Posted in wrong Place Can some Mod move it tothe correct Forum.