Spinrite, MACE utilities, etc. Lots of disk tools out there. I'll look around and see if I can find my old copy of Norton Disk Doctor. Run it from a boot floppy and you get a much finer degree of control over how the scan is performed. If you have a boot floppy with the right files, you might want to try running fdisk, blowing away the partition info and recreating it followed by reformatting.