Epson 486SX - Manual (Page 155)

Exiting the Hard Disk Format Menu
To leave the Hard Disk Format Menu, select Exit. The screen
displays the Operation Menu.
If you formatted the hard disk with option 1 or 2, you must
now install MS-DOS (or another operating system) on the hard
disk to prepare it for use. Remove the Reference diskette from
drive A and then follow the instructions in your operating
system manual. The installation process automatically
partitions and formats the hard disk.
If you ran only the Non-destructive surface analysis, remove
the Reference diskette from drive A and press the RESET button
to load the operating system.
Physically Formatting a Hard Disk A-13