Dell OptiPlex GX400 Service Manual page 13

Removing a CD, Zip, or Other External Drive
CAUTION: Before you perform this procedure, see
NOTICE: Before disconnecting a device from the computer or removing a component from the system board, verify that the standby power light on the system
board has turned off. To locate this light, see
1. Turn off the computer and devices, disconnect them from their electrical outlets, wait at least 5 seconds, and then
2. Rotate the power supply away from the system board.
3. Remove the front panel.
4. Disconnect the DC power and interface cables from the back of the drive.
5. Remove the drive bracket from the chassis drive bay you want to use.
Squeeze together the metal bracket tabs that extend from each side of the drive bracket, and pull the bracket out of the bay.
Removing a Drive Bracket
6. Remove the drive from the bracket.
Turn the drive/bracket assembly upside down and remove the four screws that secure the drive to the bracket.
Removing the Drive from the Bracket
"Precautionary Measures."
"System Board Components."
remove the computer cover.