In computer troubleshooting, determining if you have a bad motherboard takes time and cannot just be done with a simple check or test. To determine if you have a bad motherboard, you must take several steps that follow the classic computer troubleshooting model. You will be required to consider each piece of hardware and narrow down the problem. It's only through the process of elimination that you can be sure you have a bad motherboard.
Remove everything you can. Pull out all the cards installed on the motherboard. Leave the video card if you have one. Test and see if the computer is powering on and working. Remove other add-on pieces and peripherals until you have nothing left but the basics, that includes the motherboard, memory, CPU, hard drive and video card. Take out the hard drive and even the video card if it is on a card. At some point, the motherboard should appear to work, if not proceed to the next step.
Reseat the video card and hard drive. If this does not help, take out and reset the CMOS battery. Usually there is a jumper marked on the motherboard that you will have to remove. After removing the jumper, take out the CMOS battery, restart the computer and then turn it off and reinstall the battery.
Put your CPU in a good computer. If everything else fails, it will come down to either the problem is the CPU or the motherboard. Test your processor in a good computer or try replacing the CPU with a good one.
Replace the motherboard. If you have gone through all the other stpes, than your motherboard is most likely bad and the final test is to replace the motherboard and see if this fixes your problem.