New Build- problem?/HELP!

[biomodd]

I searched and didn't find anything on this...

New system powers on, but shuts down randomly. Does not stay on long enough to load the OS- whattaya guys think?

CPU temps are 36c
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Asus A8N32-SLI Deluxe nForce4 SLI Athlon 64(FX)/Athlon 64 X2
Thermaltake W0073RU PurePower PST520W Series 520W Power Supply w/Active PFC AMD Athlon 64 FX-60 Processor Socket 939 Retail
Corsair TWINX2048-3500LLPRO 2GB Kit DDR433 XMS3500
BFG GTX 512 (1)

 

[Bona Fide]

Power supply isn't good enough...
Hard drive is corrupted...
RAM is unstable...

It could be one of many things. Check them all individually.