D'oh.. edit..
Just in case, but have you already re-seated the CPU and RAM?
Can't say I'm enthused about the brands, but eh. I honestly don't think the PSU is the problem. I think the mobo is the one saying 'nuh uh.'
Case in point to what CP said, I'm running a 7900GT with a dual core proc, two 7.2K rpm harddrives, SB-XFi, AND yanking power for LEDs via USB for my keyboard mouse and joystick. All this from a supposedly 250 watt PSU. (Dude, I can't kill this Dell!) Eh, still relevant.
Do you have a Windows CD in the drive when it's doing this boot disk yammering?