Follow the procedure in Before working inside your computer:
Save and close all open files and exit all open applications.
Shut down your computer.
Turn off all the attached peripherals.
Disconnect your computer and all attached devices from their electrical outlets.
Disconnect all attached network devices and peripherals, such as keyboard, mouse, and monitor from your computer.
Remove any media card and optical disc from your computer, if applicable.
Remove the side cover.
Remove the front bezel.
Remove the 2.5-inch hard drive if applicable.
Remove the 3.5-inch hard drive if applicable.
Remove the disk-drive cage.
Removing the Power Supply Unit:
Disconnect the power-supply cables from their connectors on the system board.
Un-route the power-supply cables from the routing guides on the chassis.
Remove the three screws (M6-32) that secure the power-supply unit to the chassis.
Slide and lift the power-supply unit off the chassis.
