Anyone remember FixDisk? I used to get annoyed by utilities that would "fix" bad sectors on a disk by blanking them or just "fix" the CRC leaving the data bad. Fixdisk allowed you to (amongst other things) find bad tracks and then repeatedly read them, displaying the data received in a hex window. By observation you could see when the dodgy track had been read ok, format just that track and write the (good) data back. Disk actually FIXED! Cool.
