New PC stopped working, is it borked?

I recently got this PC:
Asus P5E iX38
Q9450 2,66Ghz
Scythe Ninja PLUS Rev B
TWIN2X4096-6400C5DHX x2, a total of 8GB
Radeon HD3870 512 GDDR4
2x Seagate Barracuda 7200.11 500GB 32MB Cache
Corsair 620HX
Windows Vista Home Premium 64-bit (fully updated)
I picked the parts and had a site assemble it, test it and send it to me.

The first time I tried to play COD4, the PC restarted after a few mins. I thought my GPU might be overheated so I used RivaTuner to set the fan speed high and tried to play again. The temperature seemed to be fine, but it still restarted. Then I used MemTest and I got errors almost right away. So I started testing the memory one stick at a time and got no errors. Then when I tried to start the PC with two sticks, it started to act weird. Basically, when I turn it on, the lights go on, the fans go on... then a couple seconds later, they both go off. It keeps repeating this over and over untill I cut the power. I have no idea of what the problem here could be so any help would be appreciated.

Edit1:>>>>>>>>>>>>>>>>

I'd like to reply but it just says that this thread doesn't exist if I try to. Thanks for the replies so far, but like I said, I can't change any settings or anything. After I turn the PC on, the lights and fans go on and then almost immediately go off again... and repeats this over and over. Nothing shows up on the monitor.

Sounds like you might have a bad MB. Try testing one memory slot at a time in memtest with a stick that you know is good.

Thanks for the replies so far, but like I said, I can't change any settings or anything. After I turn the PC on, the lights and fans go on and then almost immediately go off again... and repeats this over and over. Nothing shows up on the monitor.