try the following:
1. Shut down and turn off the computer.
2. Unplug the computer from the wall or surge protector (then remove the battery if it is a laptop).
3. Hold down the power button for 30 seconds to clear the software connections between the BIOS and hardware and clear any corruption in the temporary memory.
4. (If it is a laptop, plug the battery back into the laptop and then) Plug the computer back into the wall.
5. Turn it on to reinitialize the software connections between the BIOS and hardware.
6. If it now starts, do steps 7-9. Otherwise, report back.
7. Go into your BIOS and load default settings to clear the CMOS memory.
8. Save Settings and exit the BIOS.
9. Run 1-5 again to reset software connections between newly reset BIOS and hardware.
The above has been known to fix issues similar to the one you are describing. Good luck!