Here is a helpful guide on how to safely create a NAND backup and what you need to know.
Think of the Wii’s NAND flash memory as its brain and its heart. It’s the internal storage chip (the 512MB one) that holds everything unique to your console: nand backup wii
: The Wii will begin reading its NAND. It is common and normal to see "Bad blocks" during this process; the software is designed to handle them. Here is a helpful guide on how to
Once the process is complete, remove your SD card and put it in your computer. You will see a new folder on the card. nand backup wii