No Post or display on startup

Hi Everyone I am building up a computer from old parts and have hit a brick wall. I have tested all parts ( except m/b and cpu). I cant get post or any display from onboard video or a working video card. The hard drive spins when not connected to m/b, power only, as the same as the dvd rom. As soon as I plug the ide cables (from the dvd/HD to the m/b) they wont power. I have run the set up out of the case with a diferent PSU ( to check for m/b shorts) and get the same results. Could I have a faulty m/b, cpu or both? Any ideas would be great.

It's very rare for the CPU to be faulty, I would point to the motherboard first. Troy

ok I will try replacing the m/b Cheers