Dell OptiPlex 5050 Small Form Factor Owner's Manual page 31

c optical drive [3]
d Data cable [4]
5 Disconnect the following cables and screw from the system board:
a PSU [1]
b hard drive and optical drive caddy stand off screw [2]
c PSU [3]
d power switch [4]
e intrusion switch [5]
Removing and installing components 31