The PC I'm putting together for my brother: C2D 6400, Biostar TForce 965pt, PQI Turbo DDR2 667 RAM, and NVidia 7900gs, refuses to POST. The power is on, the fans spin, but everything shuts down a few seconds after powerup, only to restart after a second or two. There's no POST beep of any kind, and no image displayed on the monitor. I've tried swapping a working ATI x800xl, to no effect. I've also tried running the PC with only the RAM and CPU installed, and with just the CPU, but I still can't get POST. Help!