Troubleshooting: My computer won't turn on
http://support.apple.com/kb/TS1367
Resetting the Logic Board
Resetting the logic board can resolve many system problems. Whenever you have a
unit that fails to power up, you should follow this procedure
before replacing any modules.
1 Unplug the computer.
2 Press the Power On button on the front of the unit.
3 Open the side access panel.
4 Remove the battery from the logic board.
5 Wait at least 10 minutes before replacing the battery.
6 Make sure the battery is installed in the correct +/-
direction.
7 Reassemble the computer and test the unit.
Cheers, Tom 😉