Content by William R. Walsh, original here.
1. Turn off the computer (system unit and all attached options, such as the printer).
7. Lift the bottom cover approximately 25.4 mm (1.0 inch).
CAUTION: Remove the cable from the cable hook as you lower the bottom cover to prevent damage to the system. (Editor: Don't just let the bottom of the system unit fall as you tilt it out without releasing the cables. If your cable hook is loose in the system, then you can let the system's bottom cover down without releasing it.)
8. Swing the bottom cover out and down. The system unit is now ready for you to install internal options.
To re-assemble the system, perform the steps above in reverse. Make sure the power and display cables that plug into the system board are out of the way of everything in the bottom half of the case, or you might damage them. Put the cables back into the cable hook if it is still attached to the top of the system.
If the Cable Hook Falls Out
When opening your Model 25, you may notice that the cable hook that holds the power and display cables is no longer attached to its correct place in the system. Although this is not a big problem, it does increase your chances of pinching the cables when you reinstall the bottom cover.
The cable hook falls out after a number of years because the adhesive pad it is stuck to loses its stickiness.
To fix this problem is easy. Simply remove the wires from the cable hook, put some super glue on the cable hook and cable hook pad. Press both together and allow them to fully dry. Reinstall your cables into the cable hook, close the bottom cover of the system, and you will have fixed the problem.