My approach to troubleshooting would be to remove everything bar the CPU and 1 stick of RAM (I'm assuming there's onboard VGA) and see what happens. Assuming that you have thermal paste on the CPU, to be certain.
If you get that going, take it from there.
If not (and you have already verified the CPU), try a different RAM module, and if that doesn't work, it's a faulty mobo.
SD