Instructions
Go to your GameCube's "Memory Card Screen." Select with your control stick a file that you wish to delete or move and then press the "A" button.
Select "COPY," "MOVE" or "DELETE" as your action and then press the "A" button again. If copying or moving files, make sure you have another memory card plugged into the console and that the secondary memory card has enough space to store the transferred file.
Hit "YES" with your control stick on the action confirmation window that pops open and then press the "A" button to confirm. Keep in mind when copying or moving files that if your secondary memory card already has a copy of the file or the transferring files contain locked system information, then the files will not transfer.
Pick "Memory Card Screen" from the main menu if you believe that you have a corrupted memory card. If the card does not automatically reformat upon selection, confirm on the pop up window that the card needs formatting by selecting "YES" with your control stick. Press the "A" button and reconfirm using the previous method on the secondary formatting confirmation window.