I have a dual core and it don't post any more my guess is the motherboard is gone.

The fan on the cpu spins and the hard drive powers up but no bio screen or anything.

Any beeps?

What memory do you have in the system? If it's a single stick of RAM, try moving it to a different slot. If you've got two sticks in, try putting in only a single stick of ram and move it about the different slots.

I've got a Pentium D and had exactly the problem you described (no beeps, no POST, no video signal at all, fans spun and everything else started up). Turned out the memory slot on my board was dead, moving my ram to another solved the problem and I've been running fine since then (I do plan on replacing it at some point with a Core2Duo board + CPU, but, it works for now!).

It could be the CPU too as that is the same behavior as when the CPU is dead. Are there any diagnostic LEDs on the motherboard? Or beep codes?

no beeps nothing it booted up once then nothing it locked up in the bios on the first boot.

It sounds like it is either a problem with the motherboard or CPU as it wouldn't boot the first time if it was because of a memory incompatibility. I've seen the exact same thing happen on a server where the heatsink wasn't making full contact and the chip burnt out a few seconds after the first boot. Do you have another CPU you can try in the board?

yes but would have to tear apart my pc and it's not worth it to see if it's the m.b or cpu I was going to buy a new M.B and if that was it then i'd be happy

Out of curiosity, did getting a new motherboard fix it?

Yes this can happen but it does not always cook the cpu completely. Sometimes it just thermal trips the cpu but it sounds like something is cooked for sure.

Did getting a new motherboard fix the issue.

Have you solved the problem? If not: try to minimize the "failuresources". Unplug the disks and optival drives, remove all cards except your VGA. Then try again.