Dell OptiPlex E1 - Manual (Page 55)

Eject-, Power-, and Reset-Button Removal (Mini Tower Chassis): Dell™ OptiPlex™ E1 Systems
To remove the eject, power, and reset buttons, follow these steps:
1. Lay the front bezel on a flat work surface with the back of the bezel facing up.
2. To remove the 3.5-inch diskette-drive eject button, pull gently on the plastic part of the button until it comes free.
3. To remove the power button or the reset button, use a small screwdriver and push in on the 2 or 3 plastic clips that hold the button to the bezel.
When these clips are released, the button comes free from the bezel.