Here is something I wrote up a while back. If nothing works take the CPU off and reaseat it. I had trouble with an Asus A7N8X a while back and when I reset the BIOS it worked fine.
Motherboard will not Boot.
Everytime you work on the motherboard, turn the computer off all the way and unplug it. If you have it plugged in you still have electricity flowing into the motherboard. You can damage some ports like the PS2 keyboard or the hard drive ports, or the PS2 mouse port.
The remedy for this varies . . . .
BIOS:
BIOS may be improperly set up. Turn the computer off completely unplug it and then use the procedure in your manual to reset the BIOS to factory defaults. Sometime you have to remove the battery. Do not remove the battery unless you have to. Once you damage the battery holder, the motherboard is useless!
Grounding Out the Motherboard:
Make sure the motherboard does not touch any metal surface in the case. Sometimes a mounting post will come up in a place that does not line up with the holes for the motherboard. If it does the motherboard will ground out. Also the motherboard is not screwed directly onto the mouning plate. Some people have tried this! You must use metal or plastic standoffs to mount the motherboard.
CPU Fan and Cooler:
The fan from the CPU cooler must plug into the fan header on the motherboard meant for the CPU fan. If not the motherboard will not start. The cooler must be LEVEL and LINED UP CORRECTLY for your CPU and socket. The cooler must also have either a thermal pad or some thermal paste like Arctic Silver to transfer the heat from the CPU to the Cooling fins. Sometimes on older computers dust collects in the fins and the cooler can no longer work effectively.
Memory:
Memory could be damaged or installed improperly. It must be firmly pushed into place till the locks on the side click down into place. Try removing the memory dimms and then pushing them back into place. Some corrosion may build up on the contacts. Sometimes memory has to be installed in specific banks or in the right order in the available empty slots. One stick of memory could be bad, or all of the memory can be bad. Try booting with only one stick of memory if possible.
I/O Boards:
VGA, Video, Sound, Network, etc:
With the cards you may have to remove a screw to adjust how they sit in the slot.
VGA or Video Card:
The video card may not be seated in the VGA slot correctly. simply pull it up and push it back in to seat it properly. Memory can be bad on a video card. Make sure the monitor is plugged in correctly and the plug is screwed down at least finger tight. Do not try to tighten it down too much; just barely screw it down with your fingers only. If you have an old video card try another one.
Drives:
Connect just a floppy to test the motherboard with an old boot disk. Just using a CDROM drive works too on newer motherboards. It is ideal to have as few things in the way as possible when you test the motherboard. The fewer things connected, the fewer things there are that can go wrong. Also if the motherboard is bad, you will not have to remove all that extra stuff to take the motherboard out of the case.
Power Supply:
The power supply may be dead. A power supply has several lines at different voltages it takes to run a computer like +/- 12 volt, +/- 5 volt, and +/- 3.3 volt. If just one of these lines is not good then the power supply is bad. Each line has a different number of Watts and Amp rating. When you add them all up you should get the watt rating of the power supply or close to it. The options for power up on mouse activity or keyboard activity use some of this power as well. The USB may also have this option to power on after some activity.
Last Ditch Effort:
When all else fails remove the motherboard and set it on a piece of cardboard or non-conductive surface. The silver bag it came on may not be non-conductive, so do not use that. The top off the cardboard motherboard box is ideal, but you may not want to cut it off if you have to send it back. So put the motherboard on the cardboard. Then with the CPU and the memory in it, attach a power supply. Plug the power supply in. Take a screw driver and touch the two posts that the power switch connects to. The motherboard fan/CPU fan should spin up and the motherboard should become acitve. It will probably beep for no monitor or no operating system. If it does not beep or give you a verbal message you should call your supplier for permission to send it back. Usually you have to fill out a form and get a RIN number to send it back.
If you get a good result like a beep or a message, try attaching a video card and a monitor and see if you can get into the BIOS. If you can the motherboard may not be bad. It may have just been grounding out to the case.
If you do not like my post feel free to point out your opinion or my errors.
