Dell OptiPlex Gxi - Manual (Page 117)

System Power-Supply Removal (Midsize Chassis): OptiPlex GXi
To remove the system power supply, follow these steps:
1. Disconnect the AC power cable from the back of the power supply.
2. Free the system power supply from the securing tab labeled "RELEASE -->
, " and rotate the power supply to the right until it stops.
3. Press the securing tab to the left to release the system power supply.
4. Disconnect the DC power cables from the system board and the drives.
5. Lift up the front end of the system power supply, and move it to the right to disengage the system power supply from the slot in the chassis.
6. Lift the system power supply from the computer.