Instructions
Power on your Wii. Select the "Wii Options" button in the lower-left corner.
Select "Data Management." Select "Save Data."
Select the block(s) of data you wish to delete. Click "Erase." Repeat for additional unwanted blocks. If you have data on an inserted SD memory card you wish to remove, select the "SD Card" tab.
Click "Back" to exit out of the Wii Options menu.