PS2 Sony Memory Card corrupt- what should I do?

I lost my old memory card and bought a used one the other day. It didn't work, was just a crappy off brand. I returned it for a used Sony one. I started by going to browser to delete the old files, just a bunch of crappy sports games. Anyway, there were a few corrupted files on there, which got me nervous. I tried deleting them but it kept saying "Delete Failed" so they're stuck :o

Is it ok to use this card? Or could it possibly harm my PS2? Also, could my saved games on it be corrupted too? How exactly does a file get corrupted? Does it just happen or is it the fault of the player?

Thanks for any help.

Apart from the fact that the corrupt files are taking up sapce, it should work fine.

But since you bought it used, take it back and complain. you should get another card or your money back