Shut down your operating system, remove any media (diskettes, CDs, or tapes) from the drives, and turn off all attached devices and the computer.
Unplug all power cords from electrical outlets.
Disconnect all cables attached to the computer. This includes power cords, input/output (I/O) cables, and any other cables that are connected to the computer.
Remove the thumbscrews from the rear of the computer and slide the cover toward the rear of the computer.
Cover installation and connecting the cables After working with options, you need to install any removed parts, replace the cover, and reconnect any cables, including power cords and telephone lines. Also, depending on the option that is installed, you might need to confirm the updated information in the Configuration/Setup Utility program.
To replace the cover and connect cables to your computer:
Ensure that all components have been reassembled correctly and that no tools or loose screws are left inside your computer.
Clear any cables that might impede the replacement of the cover.
Position the cover over the chassis so that the front edge is approximately one inch away from the front bezel.
Lower the cover down over the chassis so that the rail guides engage the rails.
Slide the cover forward. You might need to lift the front of the cover slightly to align it properly.
Insert the three thumbscrews into the holes in the cover and the chassis and tighten.
Reconnect the external cables and cords to the computer.