DUBBELDOS: Backing up 13 sector disks by Paul Schlyter You could run my little utility "DubbelDOS": run it on an unmodified version of Apple DOS 3.3: it will remove the FORMAT command, and then patch DOS 3.3 so it recognizes both 13-sector and 16-sector disks, switching automatically as needed. With DubbelDOS installed, you can use FID to copy files to/from 13/16 disks in any combination (13==>13, 13==>16, 16==>13, 16==>16). With DubbelDOS you'll lose the ability to format floppies though.