NEC POWERMATE PROFESSIONAL 9000 User Manual page 168

NOTE
anchor one hand on the rear of the system unit as
you slide the cover.
Pull the top edge of the cover out about one-half inch
6.
from the top of the chassis (see arrow 1 in the figure
below).
Lift the cover up and away from the system unit (see
7.
arrow 2 in the figure below).
Repeat this procedure if the other side cover must also be
removed.
To replace the cover, see "Replacing the Covers."
5-6 Installing Options
The cover fits tightly. You might need to
Removing the system unit cover