Start from scratch.
Using a sturdy table set the motherboard on top of the original antistatic bag it was shipped with and then set the motherboard/antistatic bag on top of a bath towel folded in half.
Remove the CPU and any thermal paste.
Re-install the CPU carefully making shure it's sitting flat on the socket before locking it down.
Re-apply some fresh thermal paste (a small drop of Artic Silver spread around with your finger inside a plastic bag) and then mount the heatsink/fan.
Remove the RAM and re-install by pushing down until the latches lock by themselves.
Install the motherboard in your case.
Using new cables, connect one optical drive to the secondary IDE and one hard drive to the primary IDE (unless it's SATA, then connect it to SATA 1).
Connect power to everthing but don't boot yet.
Check the owners manual for the motherboard on where to find the jumper to reset the BIOS.
Reset the BIOS acording to the manuals instructions.
See if the motherboard will post.
I have a SOYO board that used to do that every so often..............until I did the above and it has'nt done it since.
Good luck!