new Computer wont start

[atzz]

Hello, I am building a new computer and I can not get it started. I have built other PCs before but have not encountered this problem before. I put all the parts together and when I try to boot up I see the option to enter the BIOS, a few seconds later the computer shuts down. I also hear no POST(no beeps) Here is my setup:
Asus P5N-E SLI Socket 775
Intel Core 2 Duo E6750 Socket LGA775 2.66Ghz
OCZ DDR2 PC2-6400 800MHz Platinum XTC 2GB
BFG GeForce 8800 GTX OC nVidia GeForce 8800GTX.
Antec Quattro 850W High Efficiency 80 Plus Power Supply

I tried all the obove parts in an other computer and they worked fine. I did not test the CPU or MOBO on another comptuer. I also have a radeon x700pro to sub and corsair 2x512MB DDR2.

Thank you in advance for all the help.

[CodyH]

Is there an LED on the mobo?
If so, when you plug the PSU into it, does the LED come on?

[atzz]

CodyH, I am only aware of 1 light on the mobo and it is the SLI light, and yes it lights up.

[CodyH]

Did you notice if the CPU fan is spinning?
Wonder if it could be over heating...

[disophisis]

Have you tried just using the cpu (and heatsink/fan) on the motherboard and turning it on? If it comes on with just the cpu and stays on, go from there and see what happens.

[atzz]

Yes the CPU fan is spinning. Im not quite sure how the cpu can be overheating. Its new. No OS is loaded or anytthing.

[atzz]

Diso, sounds good, ill try just that and connect all the other parts in one by one.

[CodyH]

Diso's suggestion of process of elimination is a good way to go
My money is on the mobo though... Would you be able to try your PSU in the other machine you tried the parts in, just to get that out of the puzzle?

[atzz]

I tried the PSU on another machine and it worked fine. I exchanged the mobo once already, the store tested it also and declared it dead. I used the mounting screws also, so i dont think it could be shorting out, but it might be.