When these kinds of problems occur I generally follow this protocol:
1) if your computer will boot to a point where you can enter the BIOS then do so and just exit (without changing anything) and save the settings.
This generally 'resets' a confused BIOS and in many cases will start:
If this is successful then great... if not then try (2)
2) Again this assumes you can boot to the bios, Enter the bios and remove the bios virus checker (usually under the advanced settings) and then exit saving the settings and reboot
if this is successful then great (again!) else try (3)
3) Find the appropriate jumper to short out the bios therefore resetting it (on many motherboards it is the jumper that you had to change after hours of swearing at the machine when you built it because it didn't work as it was set incorrectly!) This is usually a 3 pin jumper where the jumper is usually over pins 1 and 2. ENSURE THE POWER LEAD IS NOT CONNECTED as it can fry the bios chip completely (there is enough static in the board to short it with no additional power). Move the jumper to pins 2 and 3 for ~2-3 seconds then return it to the original place and plug in and turn on
If this is successful then your back in business (however you may have to play with the bios settings to get it to recognise drives and peripherals again) else goto (4)
4) Remove the bios back-up battery (the big silver watch style battery) for around 10 minutes and then replace it switch on and see what happens. as with option 3 you may need to reset the bios setting as they will be restored to factory defaults.
If this works then yippee if not then try option (5). HOWEVER this should only be tried by a trained professional!!!!!
5) Find the biggest hammer you own and beat the hell out of the motherboard as it is completely dead and at least you can vent your anger before buying a replacement and having to set it up!
Hope this is of use.
