Epson 486SX - Manual (Page 177)

If you do not prepare the drive correctly, you cannot store data
on the disk. For example, if you partition the drive and format
it for MS-DOS (or for another operating system) but you do not
copy the operating system to it, you will not be able to load the
operating system from the hard disk.
If you are sure the hard disk was installed properly and you
prepared it for use as described above but you cannot access
the drive, verify that you performed each step in the
installation process correctly for your configuration.
If you cannot identify the problem, consult your dealer.
Accessing Data on the Drive
If you have been using your hard disk drive successfully for
some time and notice a reduction in performance, the data on
the disk may have become fragmented. You may want to back
up all your data and then use a disk compaction utility to
reorganize the files on your disk. Contact your dealer for
information.
If you still have trouble with your hard disk, you can back up
your data and physically reformat the disk. Then you’ll need to
reinstall the operating system and copy your files back onto the
disk. See Appendix A and your operating system manual for
instructions.
If you cannot access data on your hard disk or you are
receiving read/write errors, the disk may have a physical
problem. Contact your dealer.
B-22 Troubleshooting