My computer wont turn on, when i plug it in the light for the lan comes on, but once i push the power button the case lights come on then go off, as well as the CPU fan starts up and goes off. I assumed it was the power supply so i changed it out put im still having that problem, i tried disconnected the extra things and and reseting CMOs and still nothing happen.

FYI When i received the computer the CPU fan had fell off and warpt the the mount causing me to have to send for a new MB once i got it had to switch the CPU over, i dont know it the CPU ever worked but im betting that its cause of the CPU the comp doesnt start up??? please help me with this, im been up all night troubleshotting, lolz, but yeah

Hey, i just bougt a barebones computer to put together, Its a AMDXP 2600 on a MSI Via Kt600 with with 512 ram and a Nvida 5200 card.

Welcome to TechSpot

Are you talking about 2 PCs here, one where the fan fell off, and one to be built from the components you mention at the end?

Assuming they are 2 PCs, let's talk about the one where the fan fell off. You say you got a replacement MB (as in MotherBoard?).
Did you put thermal paste or a thermal pad between CPU and cooler? It sounds as if you CPU overheats instantly when you switch it on, it will automatically switch off to prevent damage.

Yeah Im talking bout the new motherboard, umm i dont know much bout the fan but i think its pretty cheap, lolz. Umm yeah theres a bit of therma glue there already from the install so i didnt put anymore on it

There is your problem! Re-using an existing pad, or old thermal paste does not make for a much-needed proper contact between CPU and cooler.

Go buy a tube of Arctic Silver 3 (one of the best). Failing that, any other brand will also do.
Then follow the instructions here:
http://www.arcticsilver.com/arctic_...nstructions.htm

Make sure to clean the CPU and bottom of the heatsink first properly, without making any scratches on either surface.

A search in this forum will tell you how to do the cleaning best.

sounds like the mobo wires could be atcched wrong...the cpu isnt gonna heat up in .2 seconds.

Actually, it could....very easily. A friend of mine, not having built a machine in many years and not used to the quick heat-up of newer chips, powered-up a board with an Athlon MP 1.2GB chip and no HSF. A second later, the system was down, the processor too hot to touch and burned right out (after testing with the proper parts in place). Needless to say....he's never done that again.