Compaq 247320-003 - Deskpro 4000 - 5166 Model 2500/CDS Reference Manual page 125

To install optional drives, you must remove the front bezel to
gain access to the drive cage.
To remove the front bezel, 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 and any external devices.
3. Disconnect the power cord from the power outlet.
4. Remove the side panel.