Instructions
Turn on your PlayStation 2.
Remove any game disc, CD or DVD from your PlayStation 2's disc tray. This will load the system's main menu as opposed to a game menu.
Insert the memory card you're having problems with into the "Player 1" memory card reader on the front of your PlayStation 2.
Select the "Memory Card" option from your PlayStation 2's system menu. This option is always present whether the system is detecting a memory card or not.
Select the "Format" option and then the "Yes" button onscreen. This will format your PlayStation 2 memory card, allowing both the system and your games to recognize it and use it for data storage purposes.