Instructions
Turn on your Wii and navigate to the Wii Menu.
Click on the "Wii" button in the bottom-left corner of the screen.
Select "Wii Settings."
Press the "Right" arrow on the directional pad to scroll to the third page of the Wii System Settings menu.
Select "Format System Memory." A new screen will load.
Click the "Format" button. A message will appear will the process is complete. The Wii will shut down.