Fully Corrupt:
When the entire save area of the Memory Card becomes corrupt, the system will inform the player that the Memory Card is corrupt and offer to format it. The card must be formatted before gameplay begins or when the game attempts to access the Memory Card. The exact message may vary from software to software.
Follow the steps for formatting a memory card.
For specific issues with the Memory Card 1019, please click here.
Suggestion: It is always a good idea to copy your most important files to a second Memory Card as a back-up.
Data Area Only Corrupt:
When only the data area of a Memory Card is corrupt (not the entire Memory Card) the game may not detect this until the Memory Card is accessed. Once it is accessed, the game will inform the player that the file being accessed is corrupt and must be erased. The game will only delete the one file being accessed and will not format the entire Memory Card (Other saved game files on the Memory Card may be OK).
Follow the steps for deleting a file.
For specific issues with the Memory Card 1019, please click here.
Memory Card is Damaged:
If the Memory Card has been physically damaged, or has been damaged beyond repair, you will get this message. The Memory Card will need to be replaced. The system may attempt to format the card, but if it cannot it will give the error Memory Card is Damaged. There is no way to recover the game data from the memory card.
This is how you format the memory card...
Quote:Formatting a Memory Card
This procedure is only used if a corrupted Memory Card is inserted into the Nintendo GameCube.
If required, this procedure will begin automatically when you select "Memory Card Screen" from the main menu. You cannot use this procedure to erase files from a useable Memory Card.
After selecting "Memory Card Screen" from the Main Menu, if your Memory Card requires formatting, a window will appear to ask for confirmation for formatting.
Use the Control Stick to select "YES" and press the A Button
A window will appear to notify you that all data will be erased and ask again for confirmation for formatting.
Use the Control Stick to select "YES" and press the A Button.
NOTE: When you format a Memory Card, all data will be permanently erased and unable to be recovered.
I have no idea if this would be the same for GameCube memory cards on the Wii.
Here is the link where I got the above information from...