Dell OptiPlex E1 - Manual (Page 54)

Front Bezel Removal (Mini Tower Chassis): Dell™ OptiPlex™ E1 Systems
To remove the front bezel, follow these steps:
1. Press the tab release marked with the icon.
2. Tilt the bezel away from the chassis.
3. Disengage the 2 retaining hooks at the bottom of the bezel, and pull the bezel away from the chassis.