Most PCs can't read any floppy disk beyond track 79, lots of ST disks were formatted to 81 tracks or more to fit on extra data. The disk-fixing program you refer to probably only fixes some disks that have incorrect boot sectors, it won't help with non-standard disk sizes.
On PCs where it is possible to read larger disks then the easiest way to get a file off a non-DOS floppy is probably to use Gemulator Explorer:
http://www.emulators.com/explorer.htm
Otherwise you have to make an image of a disk using one of the many tools available.
