Compaq 247320-003 - Deskpro 4000 - 5166 Model 2500/CDS Reference Manual page 111

To install an optional CD-ROM drive, IDE tape drive, or
PD-CD Drive, complete the following steps:
1. If you have locked the Smart Cover Lock, use Computer
Setup to unlock the lock.
For more information about Computer Setup, refer to
Chapter 8, "Using Compaq Utilities."
2. Turn off the computer, disconnect the power cord from the
electrical outlet, and remove the computer cover and front
bezel.
3. Remove the screws securing the drive cage and slide the
drive cage forward out of the chassis.
4. Install the guide screw into the first screw hole from the
front, on the left-hand side of the drive.
Some options use M3 metric thread hardware. Extra guide
screws are provided on the front of the chassis, under the
front bezel. The Compaq-supplied metric screws are
black.