You can install a 120mm computer case fan to increase airflow into the computer to aid in cooling in a case that is designed to have a side fan. Adding a side panel fan can help improve airflow to the entire computer or adjust the airflow inside the case to blow onto specific parts. The 120mm case fan is the largest standard case fan and can be used to feed air into or out of the case.
Power down the computer and disconnect the power cable and peripherals from the case.
Place the computer on a flat working surface that is clear of carpeting or other static-producing materials.
Ground yourself by touching a metallic object other than the computer, like a doorknob.
Remove all the screws and quick-bolts attached to the computer panel with the 120mm case fan opening.
Slide the panel off of the case.
Position the fan over the 120mm fan opening and align the screw holes. The fan should be positioned to blow into the case if it is on the bottom half of the panel and position to blow out of the case if it is on the top half of the panel.
Screw the fan into the panel at all four screw holes. Stop twisting the screws when they are firm and the fan doesn't move.
Connect the fan's power cable to a power cable from the computer's power supply. You should line up the cables so they don't get tangled.
Slide the computer's side panel back on and return all the screws and quick-bolts holding the panel to their original positions.
Case fan power connectors are usually male on one side and female on the other side so they can be attached to a power source cable and additional devices. Fans use about two watts each and power supplies typically provide 300 or more watts of power. If your computer case does not have a vent and mount on its side panel for a 120mm fan, it is possible to cut and drill holes to install a fan. If you modify the case, you can add a vent cover to the outside of the case. If you increase the airflow inside your computer by adding a fan, the computer will likely accumulate dust at a faster rate. You can clean out the extra dust every few months by spraying it with a canister of compressed air. Side panel fans do not always help with cooling the entire computer depending on the location of the other installed fans. However, you can use a side panel to blow on a specific component like a graphics card or the hard drive rack to cool specific parts and prolong their lifespans.
You should always ground yourself before working on a computer. A static discharge can damage many of the computer's components.