Computer Freezes Randomly

I've just built my computer and every went fine with the OS installing (Vista 64-bit), After running my computer with no problem. So i installed the rest of the things i need (MB, GC, and etc..). After a little bit in like 1 hour period after the installing of everthing i tried to run games like Fallout . then it froze on me... after that it freezes out of random anywhere, browsing on the website(rarely), leaving the computer(occasionally), playing game (unpredictable), starting the computer entering the desktop(sometimes), and more
My specs are
Processor: Q6700
MB: Asus P5Q
Ram: Cosair 2 X 2gb
Power supply: Cosair 650w
GC: 9800GTX+
HD: Seagate 500GB 7200.11

The temperate
CPU: 33C -> voltage 1.12V (auto)
MB:29C
GC: 33C
HD: 31C

I dont think its overheating...
All setting in bios i left it auto
Additional once the computer restart itself never happen again
The DVD drive made loud clicking noise o.0 so i open took the CD out

Yeah.....I cant find a way to fix it -.- (My big brother said it was RAM's voltage which is left on auto)

The rams are the Dominator 1006mhz 5-5-5-15 pc8500 TWIN2X4096-8500C5DF

I've read from a forum before that u need 2.1v for the ram but i cant confirm that