Rebuilt computer is not booting

[Oofgeg]

I replaced my motherboard, cpu, and memory after my computer would not work, and after setting everything up it will not boot. The light on the motherboard is on, but when I try to boot it the fan on the cpu cooler spins for half a second and then stops. I tried it with 2 hdds and 3 power supplies but same result. HELP!

 

[Steemax]

Open up your mobo manuel, and make sure all jumpers are set correctly.

 

[A True Folder]

Which brand and model board??

EDIT: OK, seems as how you logged off without replying I'll leave another question for you, have you plugged in the 4 pin ATX power (assuming you need it, I have no idea as you didn't state which board you have and my crystal ball is broken today)

 

[Oofgeg]

Sorry, the keyboard I was typing this on wasn't working right so I didn't want to type too much.

I have:
ASUS P5N-E SLI LGA 775 NVIDIA nForce 650i SLI ATX Intel Motherboard
Intel Core 2 Duo E6750 Conroe 2.66GHz
XFX 7600GT
Not sure of the harddrive brand/model, came with the prebuilt.

 

[Neodude1123201]

Are you sure its not the motherboard acting up?

 

[A True Folder]

Sooooooooo, do you have the 4 pin atx power connected???

The symptoms you describe are classic for it not being plugged in

 

[Oofgeg]

That is the one next to the CPU right?

 

[A True Folder]

That would be the one, up in the top left corner.

 

[Bahawolf1]

The 4 Pin connector comes from the power supply and plugs into the motherboard.

... as an example.

 

[A True Folder]

I'd bet that was the problem, he's plugged it in and it booted and he is now installing Windows or whatever, anyway I'm not sitting here waiting for a reply any longer, I'll check back later.