Option 1: Shut down the system, unplug it and hold the power button down for 15-20 seconds. Attempt to boot.
Option 2: Shut down the system, unplug it, remove the CMOS battery and set the jumper to Clear CMOS, hold the power button for 15-20 seconds, move jumper back to standard operation, insert battery. Attempt boot.
If neither works, shut down the system and unplug it, remove your RAM, plug in the system and power it on. If no sound is made, high chance of bad MB. If it beeps at you, power it down, unplug it and insert your RAM testing each stick one at a time.
Hope this helps.