Although there are no moving parts in your computer after the power cord has been disconnected, the following warnings are required for your safety.

Keep fingers and other parts of your body away from hazardous, moving parts. If you suffer an injury, seek medical care immediately.

Disconnect all power cords from electrical outlets before removing the computer cover or any part that has the above label attached.
DO NOT disassemble components that have the above label attached. There are no serviceable parts inside these components.
Your product is designed for safe use. However, hazardous voltage, current, and energy levels are present inside any component that has this label attached. Disassembling of these components might cause fire or might even result in death. If you suspect a problem with one of these parts, contact a service technician.
Prepare your computer. See Preparing your computer.
Disconnect the power supply assembly cables from the system board and all drives. See Parts on the system board.
Release the power supply assembly cables from the cable clips and ties.

Ensure that the new power supply assembly is the correct replacement.
Install the new power supply assembly into the chassis so that the screw holes in the power supply assembly align with those in the chassis.
Connect the power supply assembly cables to the system board and each of the drives.
Secure the power supply assembly cables with the cable clips and ties in the chassis.
To work with another piece of hardware, go to the appropriate section.
To complete the installation or replacement, go to Completing the parts replacement.