GameCube memory cards are used with both Nintendo GameCubes and Nintendo Wiis to store GameCube game data. However, with the use of an SD card and a special adaptor, a homemade GameCube card can be created which will not only store GameCube game data but allow you to transfer that data to other devices, such as a PC.
Insert the SD memory card into your GameCube SD card adaptor.
Insert the adaptor into the memory card slot on your GameCube or Wii. This slot is on the front of the GameCube and on the left side of the Wii.
Insert a GameCube game into your GameCube or Wii and begin playing. When you are ready to save your game, do so in accordance with your game's saving procedure and the information will be transferred to your new GameCube memory card.
If you wish to transfer your game information to a PC, you can do so by removing your SD card from the adaptor and inserting it into your PC.