If it occurs only with one or two diskettes, there may be a problem with
those disks and not the drive. If this problem only occurs when using disks
of a certain brand or density, consider trying another brand of diskette.
If a given diskette produces the same error in another computer, then
almost certainly the problem is with that disk.
However, if this happens no matter what disk you insert - even master
application disks - the problem most likely is with the disk drive itself.