Instructions
Back up your save data and channels by going to "Settings," then "Data Management." Insert a formatted SD card, then select "Wii Channels." Select a channel and choose "Copy." Channels have to be saved one by one. You can select all save data (under "Save Data" in "Data Management") and copy it simultaneously.
Remove the SD card, then return to the "Wii Settings" page. Navigate to page 3. Click on "Format Wii System Memory." On the next screen, click "Format" to confirm, then wait until the system restarts. This means the format change is complete.
Insert the SD card, then return to the "Data Management" screen under settings. Select "Save," then select "Wii." Select the SD card, then copy the contents of the card over to the Wii.