First of all, check if there are any inflated capacitors, if there is even one- ditch MBO, other capacitors will soon follow. If no inflated capacitors proceed with these diagnostic steps: 1/ disconnect all peripherials (DVD, HDD, card reader...), leave only MBO, PSU and RAM (and CPU of course); if nothing happens 2/remove CMOS battery (CR2032) for 20-30 sec with power cord disconected from computer, that will reset BIOS; 3/ take out RAM sticks, then, if you have more than one stick, try with each stick separately (it might be faulty RAM); 4/power on MBO without any RAM-if speaker is present it should give BEEP signals; 5/ try with different PSU, many power supplies are faulty even when they do give power to MBO.
If nothing of above does not help than you have faulty MBO, because CPUs are so rare to fail that in my 10 years of experience in PC service I had 3-4 fried CPU-s, and even that was because costumer tried to clean PC, removed CPU cooler and than incorrectly placed it back or didn't put thermal paste afterwards.