Computer runs for a few seconds then stops

[Spacedomo]

Hello,
Finally, after hours of building, it's time to plug in the computer and test the power supply. After plugging in the CPU, I flipped the switch on the power supply and pressed the power button on the case, the LEDs lit and the fans ran, but this all only lasted about two seconds. If left alone, the computer will repeat this again and again. I tried all sorts of plugging arrangements with all the parts, but to no avail.
Convinced it was the power supply, I sent it back for a replacement. I'm building a computer for gaming, so I figured 850 watts would be enough. If the power supply isn't the problem, any ideas on what it might be?

 

[Proximon]

http://www.tomshardware.com/forum/261145-31-perform-steps-posting-boot-video-problems

 

[Proximon]

This topic has been moved from the section Forum Feedback to section Systems by Proximon

 

[smorizio]

can you toss up the parts you uses??? a lot of time it can be a bios issue with ram and mb till you uprev the mb bios..a lot of times people forget to use the standoffs...or the i\o shield is too long and shorting the mb out or the builder forgot the 4/8 pin pci power connector.