I've used a wide variety of crap disks as casual backups "just in case" and the Korg has formatted almost everything beautifully. Guess there's a place for all those AOL disks to go now, huh? Just like some folks using their old hard disks as safety dumps for some things, a spare set of Wundersounds on a vanilla 3.5 could save you mucho grief someday. The few disks its rejected have just triggered an error message in the display, so its worth a try.