Dell OptiPlex GX1p - Manual (Page 72)

Computer Cover Removal (Mini Tower Chassis): OptiPlex GX1p
To remove the computer cover, follow these steps:
1. Turn off power to the computer and all peripherals, and disconnect the AC power cables from their electrical outlets.
2. Remove the padlock if one is installed.
3. Facing the left side of the computer, press the release button at the bottom-left corner of the front bezel.
4. Lift the bottom of the cover, allowing it to pivot up toward you.
5. Disengage the tabs that secure the cover to the top of the chassis, and lift the cover away.
Before you reinstall the cover, fold all cables out of the way so that they do not interfere with the cover or with proper airflow inside the computer.