New computer not starting

Today I built an amd64 3000+. Well I've never built a computer before but I'm not a total newbie. Anyways, Everything is plugged in, and I go to hit the power button on the case and nothing happens. When I plug in the power supply to the wall, I hear a quiet but high pitched squeel. And thats all that happens. No fans spin, the heatsink fan doesnt spin. Nothing. Is there something noticably wrong here?

Also I brought it over to a friends thats pretty new as well, and we plugged in his 350w power supply to my motherboard and after about 4-5 times of switching it on and off, the power supply blew up a big blue spark.

Here are my specs and hardware that I am using,

ASUS k8t800 mobo
amd 64 3000+
corsair select 512 mb ddr
Linkworld case with a 400w power supply


Is there by any chance that I didnt put in the processor right? Like I put too much thermal paste on it? I put a very thin layer though so I don't think thats it.

It cost 65$ to have a tech look at it, so Id like to try and fix it myself. Could it be a defected motherboard? Defected proccessor?

All I know is that nothing works or spins when I turn the system on. And when I plug in the power supply cable into the wall theres that quiet high pitched squeel for about 2 seconds and stops as if it just started up or something.