Instructions
Move your cursor to the "Wii" button on the bottom-left side of the screen. Press "A" to enter the Options menu.
Scroll to "Wii Settings" (wrench) and press "A" again. Highlight the blue arrow (left side) and press "A" twice, to access Settings Page 3.
Select "Format Wii" on the bottom part of the screen, and then press "A." When the warning prompt appears, choose "Format."
If your Nintendo Wii Parental Controls are turned on, you'll have to enter the password prior to accessing this screen.