Quote Originally Posted by Azar View Post
Yeah, you have to use a PS1 memory card for PS1 games. It'll fit in the slot just fine. And you can transfer save files from a PS1 card to a PS2 for backup or safekeeping, but you can only save/load from a PS1 memory card.
Yes, that is because PS1 games do not understand the file system used on PS2 memorycards.