Epson LT - 286e - Manual (Page 127)

3. Lift off the motherboard cover.
4. Notice the outline for the math coprocessor on the
motherboard.
5. Make sure the notch on the math coprocessor lines up with
the notch on the outline on the motherboard. Press the
math coprocessor firmly into place.
6. Replace the motherboard cover.
7. Reinstall the hard disk. Insert the hard disk drive straight
down; it will not go in correctly if you attempt to press it in
at an angle.
B-14 Installing Options