Instructions
Locate the power cord on the back of the PlayStation 3 console. Unplug the cord and leave it unplugged for 10 to 15 minutes.
Plug the cord back into the back of the console. Ensure the cord is plugged in all the way as it will not boot correctly unless it is plugged in completely.
Press the power button and hold it down until you hear a loud beep after 10 seconds. The beep alerts you that the console is initiating a restarting process. The console should now be booting.
Wait for the console to boot correctly. If the process worked as intended, the PS3 should now be playable and should be operating normally.
Contact Sony customer service if the console is still not responsive (see Resources).