PC boots for a second?

I've bought new components for my PC and connected all of them (I think) properly but the problem is whenever I switch on my PC it starts up for just a second and turns off immediately!

The parts are as follows:

1- CPU: i7-860 @ 2.80 GHz.

2- PSU: Cooler-Master 500W.

3- RAM: @1600 MHz, 6G.

4- GPU: GTS 8800.

5- MB: Asus P7P55D.

I checked the wire-connections multiple times but with no luck, if any of you had a similar problem or has a suggestion please post some feedback.

Thanks in advance.

Chances are you just missed the 4/8-pin power connector.

Provides power to the CPU, so it has to be plugged in. The system won't boot unless it is; it will instead do exactly what you're describing.

Might be a psu problem, what model is it? need more info then cooler master 500w

Hmm...I assume you double checked and made sure the motherboard power connectors are secure?

Well, it sounds like you've done everything right..meaning you probably have a DOA component. It happens. Now you just need to figure out if it's your PSU or motherboard so that you can RMA it. Odds are it's a bad motherboard. Do you happen to have an old PSU lying around that you can test with?

Have you tried using only one stick of RAM? Time for my story with an issue while assembling my rig. My computer refused to post, rather it would keep booting and restarting constantly (I assumed this because the CPU and GPU fan speeds would cycle). After rearranging my RAM, I could boot the computer, and could only boot the computer if the RAM was not set into a triple channel setup. After some research, I thought perhaps one of the CPU pins on the motherboard was bent. When I took off my heatsink (Scythe Mugen-2 is a pain to get on...) and CPU, I managed to find one bent CPU pin in the towards the middle. I straightened it out, and then everything ran perfectly. So I recommend you remove the CPU, look for anything out of the ordinary, and just put it back on and see if that does anything.

Have you tried using only one stick of RAM? Time for my story with an issue while assembling my rig. My computer refused to post, rather it would keep booting and restarting constantly (I assumed this because the CPU and GPU fan speeds would cycle). After rearranging my RAM, I could boot the computer, and could only boot the computer if the RAM was not set into a triple channel setup. After some research, I thought perhaps one of the CPU pins on the motherboard was bent. When I took off my heatsink (Scythe Mugen-2 is a pain to get on...) and CPU, I managed to find one bent CPU pin in the towards the middle. I straightened it out, and then everything ran perfectly. So I recommend you remove the CPU, look for anything out of the ordinary, and just put it back on and see if that does anything.

Luminouslight

CPU fan secured properly? If it gets too hot itll shut down or blow up.

Sorry everyone, problem has been solved, it turned out that the motherboard was not properly connected and somehow it won't start up but now everything works like a charm, thanks again, I can't wait to use my new PC :Dabuabed