Is (are) the shutters of your floppy disk(s) working correctly, ie freely? It may be time to rewrite your frequently-used floppies to new diskettes. Failing that, it may be that your drive needs cleaning and re-lubricating. You puzzle me, however, with the statement that a PC drive has been handling the requirements of Mac 800kB diskettes. Or do you mean that a formerly internal drive was transferred to the external case?

de