Instructions
Power on your PSP as you normally would and then scroll all the way to the left side of the cross media bar until you reach the "Settings" area. It is represented by a toolbox icon.
Scroll down through the settings menu until you find the "System Settings" icon. Press X to bring up a new menu.
Select "Restore Default Settings" from the system settings menu. Press X. A dialogue box will pop up asking if you are sure you want to restore your default settings. Highlight the "yes" option and press the X button. The process will begin automatically.