Epson 10020 - Manual (Page 53)

If a diskette is in the drive but the latch is up (horizontal) and
you enter a command for that drive, the computer cannot tell
there is a diskette in the drive and displays an error message
such as this:
Drive A: not ready
Make sure a diskette is inserted into
the drive and the door is closed
Press any key when ready . . .
Close the latch and press any key to continue.
To remove a diskette, turn the latch up until it is horizontal
and the edge of the diskette pops out. Carefully pull out the
diskette, place it in its protective envelope, and store it in a
proper location, such as a diskette container.
Inserting a 3 1/2-inch diskette
If you have an optional 3 1/2-inch diskette drive, insert the
diskette with the label facing up and the metal shutter leading
into the drive, as shown below. Slide the diskette into the drive
until it clicks into place.
2-12 Using Your Computer