Instructions
Hold the power button on the right side of your PSP down until the device completely powers off. Wait at least five seconds after the power is off before proceeding to the next step.
Press and hold the Select and Start buttons located in the bottom right corner of the PSP.
Press and hold the Square and Triangle buttons (located on the directional pad) while continuing to hold the Select and Start buttons.
Press the power button while holding these four buttons. When the flash (logo) screen appears, you can release the four buttons and your PSP will be reset to its factory settings and the screen will no longer be blank.