Dell OptiPlex E1 - Manual (Page 38)

Eject-, Power-, and Reset-Button Removal (Low-Profile Chassis): Dell™ OptiPlex™ E1 Systems
To remove the eject, power, and reset buttons, follow these steps:
1. Lay the computer cover upside down on a flat work surface with the back of the cover facing you.
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 computer cover.
When these clips are released, the button comes free from the front panel of the cover.