Dell OptiPlex E1 - Manual (Page 45)

Expansion Card Removal (Low-Profile Chassis): Dell™ OptiPlex™ E1 Systems
To remove an expansion card, follow these steps:
1. Disconnect any external cables from the expansion card being removed.
2.
Remove the expansion-card cage .
3. Remove the retaining screw from the card-mounting bracket.
4. Grasp the expansion card by its corners, and carefully remove it from the expansion-card connector.