Instructions
Turn on your PS3 system by pressing the power button on the front face of the unit or by pressing the "PS" button in the center of one of your PS3 Sixaxis controllers.
Scroll to the left using the left analog stick on your controller. Stop on the "Settings" menu.
Scroll down and press the "X" button over the "System Settings" option.
Move down the option list and press the "X" button over the "Restore Default Settings" prompt.
Follow the on-screen instructions to complete the reset. Once the settings are restored to the default, your old private network will be removed. You are then free to set up a new network.