When I power my new custom built system on, the whole system shuts off within a second.
What went wrong?
After stripping down all the components to only a power supply + motherboard and a Q6600 processor (with its included heatsink/fan with a thermal paste already applied), the problem still occur.
I also tested the motherboard outside of the case, the problem wasn't solved.

I tried to look at google but I couldn't find any consistent information.

My specs are:
Asus P5K-E
Q6600
2x 1GB Ballistix
Seagate 500GB 7200rpm
Samsung 203B dvd drive
evga 8800GT 512mb geforce

I've never had this problem but maybe you could try the following:

Does your PSU have a switch on it for your country's AC? Is it set to the correct one? (220 or 120 etc)

Is your motherboard sensing an open chassis/case? (Not sure if this would have the same results).

Is your ram plugged in correctly? Is your graphic card plugged in correctly? (although - often the pc will stay on but the monitor might time out) Have you tried starting again from scatch and replugging/reseating everything including the CPU?

I'd start from complete scratch again and see what happens? Check connections, swap cables and connectors etc.
(and I'd follow the manual, maybe start with one stick of ram etc.) How does the psu run when it's not connected to anything? (if that's even possible).

Does the pc beep or have any leds on the motherboard or anything as a clue? Rig up a speaker and see if it gives any clues?

My PSU is a CoolerMaster 500w and it is set to 120.

I never heard anything about a motherboard sensing a open case.

Whether I run the system with one dimm of ram or not, it only runs for 1 second. But I stripped the system down to a motherboard, PSU, CPU + stock fan and tried to run that off and it only ran for 1 second.

There is a led on the P5K-E that shows if there is current on the mobo and when I connect it to the PSU, the led is lid up to show it has current.

Do you have another PSU you could try, it's that or the motherboard.

Try this. When you have everything setup, try unplugging the ATX 12v 4-8Pin connector which is near the cpu socket. I had a similar problem with recent build, and the problem was a shorted motherboard. When I would disconnect the ATX 12v 8 pin (on this motherboard), the problem would go away, but the system wouldn't boot without that power. But, by doing that I was able to isolate the problem.

Myougi did you ever figure out the problem yet there, if not keep asking around sure someone can come up with something. I am sure its a simple fix.I am having a slow annoying build here with problems dont feel bad.I am becomeing inpatienced though i wanna get this thing fired up soon.

Fire away if you are having problems. I have done a few builds in my days.

Myougi.... please update us.

well i just took everything apart and am gonna start over again, my front panel light was the only thing coming on, no beeps,no fans,and nothing on my monitor cam on. i posted the parts i am using in the new build forum if you want too see them, i know they are all compatible it could of been ram or my cpu you wasn't placed right or even one of the wire to my mobo was in the wrong place i dont know but i will figure this computer out, its my first build.

Yeah I found out the problem after rebuilding everything from scratch. I probably didn't plug the ATX 12v 4pin very well. Thank weskurtz81 and everyone

Now I'm having another annoying thing. My system locks himself by saying something about overclocking. I didn't even touch anything about overclocking yet. Let alone sometime there is no video output O_o. I will update my BIOS tomorrow morning

if your cpu fan has manual speed settings then you should raise it if not then your cpu is to fast for the mobo to handle

You built a very nice system, but cheaped out on the PSU. Coolermaster makes very nice cases, and sells junk PSU's.

You really need a quality PSU, or you will continue to have random problems. Something from the Corsair series will do well. http://www.newegg.com/Product/Prod [...] wer+Supply