I've got an old Asus A8N-SLI nForce 4 motherboard sitting in my office. It's socket 939. Used to use it with an AMD 3500+ and AMD 4400+ some time back.
Did you have an old socket 939 board die on you?
Yeah, that is i believe it is the motherboard, as it still doesnt run with just the psu and processor hooked up to it (ive tried multiple psu's that are tested and work). It worked fine for 3 years, then i brought it home yesterday, and even though it was working that morning, when i hooked it up for some reason the computer wont boot. Power will come on for a half second, all the fans will just start to turn, then bam, power off. Like i said, ive isolated the problem (made sure i ran it on a nonconductive surface too) so other than the processor this has to be it. I seriously doubt a bad processor would make the mobo behave this way.