All of the various components of your computer are connected in some way to the motherboard, so if it stops working your entire machine will be useless. Unfortunately checking a motherboard for problems is a much more extensive process than with any other part because every other component has to be ruled out first.
1. Power off the computer completely and then unplug all of the cables from the back of the case. Move the computer close to a different electrical outlet that you know for certain is working. Plug the power cable into the outlet and press the power button to see if the problem lies with the outlet or with a component on the computer.
2. Put your hand behind the power supply on the computer when it is powered and wait to see if you feel any air flowing from the fan, which will indicate that the power supply is working properly and is not the cause of the problem.
3. Turn off the computer and then remove the power cable. Set the computer case down so that the left side panel is facing up towards you. Check the back edge of the computer to see if the panel is connected to the case by a series of case screws, a twist-off thumbscrew or a metal latch.
4. Disconnect the side panel from the case by pulling up on the latch, twisting the thumbscrew off or pulling out the case screws with a screwdriver. Remove the side panel from the case and set it aside.
5. Check to see if there are any bent or burnt pins or transistors on the motherboard, which is the large flat sheet on the bottom of the case, to which all of the other components are connected.
6. Grab both sides of the plastic end of the SATA cable that is connected to the power supply and pull it out if the fan was not blowing air earlier. Remove the screws holding the power supply to the drive bay and then pull the power supply out. Slide a replacement power supply in and re-attach the screws and SATA cable.
7. Remove all of the SATA cables that are connected to the power supply a drive bays if the fan was working earlier. Pull out any expansion cards, such as video or sound cards, from the card slots on the lower left side of the motherboard. Remove the screws that hold the motherboard to the case.
8. Pull the entire motherboard out of the case carefully and set it down on a non-conductive surface such as a wood table. Place the video card back into the expansion slot if you are using one. Plug the power cable directly into the motherboard and then connect the monitor’s cable into the corresponding port.
9. Pull the processor off of the motherboard and push down a replacement processor. Use a screwdriver to press in the latch that depresses when you would press the power button on the case. Check to see if the computer powers up properly, which will indicate the problem is with the processor instead of the motherboard.
10. Power off the motherboard. Repeat the process of using a replacement unit with the RAM modules and graphics card to see if either of them are causing the problem. Purchase a new motherboard if the computer still will not power on after replacing the processor, RAM and graphics card.