Computer will not start at all.Need Help

I am building a computer for a friend. At first I had problems with power supply. I bought a better one. It booted up fine and than i pluged in keyboard into it. Computer shut off. Now when i try to boot it again, i get a green ligh on the motherboard, cpu fan spins for a second and than stops. And that's all i get. I tried another power supply from my computer but i get the same thing. Does anybody know what could be the problem?
Thank you,
Max

No. Keyboard is not connected at all now.

hey Naksimka:

Well lets start from the beginning, first reset C-Mos, if that doesnt solve the problem then start dissasembling the computer, take it down to bare essentials, nothing but the CPU, memory, and graphics card, if posts then great, if not then you know you have a deeper problem and need to do some more trouble shooting, often when it fails to post with the bare essentials then something isnt seated properly, reseat the memory, and graphics card and see if that solves the problem, get back to me and let me know.

<font color=blue> <Archer> Cant this trhing go any faster, I thought this was a Warp 5 engine?

<Trip> Yeah, on Paper... </font color=blue>

heya naksimka;

Ok lets start reassembling, reinstall the CPU, make sure and use thermal paste, and that the HSF is on flatly and firmly. Next lets put in the memory, only one module, put it on slot 1, then put in the graphics card, and plug in the atx cable to the graphics card if it requires one, then connect the main power plug to the mobo, and also the square 4-pin ATX cable into the motherboard. Now from here the computer should power up, post, and get all the way to the point of booting the hard drive and realise there isnt one and stop.

Oh and yes some motherboards are set to protect mode from the factory, to clear it you need to reset C-Mos, you can usually do this by unplugging the power cord from the PSU, then pull out the battery, then replace the battery and plug it back in.

If this doesnt work tell me whats going on with it in detail.

<font color=blue> <Archer> Cant this thing go any faster, I thought this was a Warp 5 engine?

<Trip> Yeah, on Paper... </font color=blue>

I think it might have been grounded before by a loose screw, but i removed it. Everything is lined up fine now. Still i get nothing. Is there some king protection on the motherbord that went off because of the loose screw and is there a way to reset it?
Thank you,
Max