Instructions
Scroll through the sub-menus on your PS3's main menu until you reach "Settings." Scroll down to "System Settings" and press the "X" button.
Scroll through the options in the "System Settings" menu, highlight "Restore PS3 System" and press the "X" button. You will be asked if you are sure you want to continue. Highlight "Yes" and press the "X" button.
Highlight "Full Format" and press the "X" button. A prompt screen will appear with an estimated time for completing the task, and you will be asked to confirm your decision. Highlight "Yes" and press the "X" button. Press the "X" button again when the system prompts you to restart to complete the restoration process.