HP QMS 1660E - Manual (Page 191)

Storage
Options
6-57 Printer Options
3 Remove the screws from the optional interface plate on the
back of the printer.
Save the screws. (You’ll use them when you install the board.)
You can either save or discard the plate.
4 If you are installing an internal hard disk at this time, use the
instructions in a following section, “Installing an Internal Hard
Disk,” and then return to step 5.