Things You'll Need
Instructions
Insert the flash card into the rear of the Game Boy Advance device, and plug the USB cable into the flash card.
Plug the other end of the cable into the USB port on your computer.
Open the "My Computer" or "Finder" application, depending on if you are respectively using a PC or Mac.
Navigate to the Game Boy Advance entry on the list of available drives connected to your computer.
Alternate-click on the entry, and select the "Format" option.
Choose the "NTFS" file system when prompted, and save the settings to automatically reformat your Game Boy Advance.