POST problem, plz help

Im building my friends computer and its always going fine until you boot it up ; ). When I give the power supply power, the computer it POSTs up for a couple seconds and shuts back down. I dont have to hit the power button. The interesting thing is that If I hit restart every second, the computer stays up as long as it doesnt reach the (3?) second mark. Im running a P4 2.4 on P4T533-C w/ RDRAM. The RAM is installed correctly. If I install the reset button in the power button's jumper spot, it will turn on just fine but I get no video signal and the HD doesnt spool up. The ironic/insulting thing about it is that someone once brought me their computer because it was doing the same thing and I fixed it and I cant now. Any help would be great.

Sounds like something that happened to my friend when he first put together a P4 system. His problem was no ATX 12v connector to plug in. Push power button, things turn on briefly then off.

My ghetto fabulous solution: unplug power button jumper, plug reset jumper in power jumpers position. Your reset button is your power on/off and your power button is decoration. Sounds ghetto, but yes, the power button jumper was the culprit here.

1.verify that all pwr connectors are in and tight. 2 get a volt meter and make sure the you have a grd on the power cord( a voltage potential or raw 110 feeding from the grd to the ps can cause havoc.3 check ps in a known good system. 4. check mb in a known good system. Hopefully you will find the culprit in one of those steps. goodluck...... flapperhead