Instructions
Turn on your Nintendo Wii.
Select the "Wii" button on your Nintendo Wii's "Wii Channels" main menu.
Open the "Wii Settings" menu.
Navigate to the third page of options in the "Wii Settings" menu and select "Format Wii System Memory." From the page that appears, select "Format." This will return your Wii to factory settings, uninstalling all updates that have downloaded to the console.