Instructions
Hold down the PS3 power button until it beeps twice; this will boot you into the Restore menu. Connect your PS3 controller to the system using the USB cord in order to navigate the options available. You should see six options in total.
Select the "Restore Default Settings" option. If your corruption is in the operating system or the firmware, restoring should repair the damage without removing any of your personal files. It will, however, take everything in the user accounts back to defaults.
Check to see if your PS3 is booting and allowing you access to your game data. If it will not, there's a good chance the issue is in your personal data or with the mechanics of the hard drive itself, and not in the system settings. If you can access the system menu from your user account, you can try to use the backup utility to retrieve what data you can.
Boot back into the Restore menu, again holding the power button down until it beeps twice and takes you into the menu.
Select "Restore PS3 System" and follow the on-screen instructions to completely format your PS3 hard drive. This will delete all the data on the hard drive and reinstall the PS3 operating system.