System Unit Care
The system unit or case doesn't require much maintenance apart from removing dust. You should, however, do some preventive maintenance activities inside the case. Make sure that the power cord is removed and carefully remove the case cover. Look inside the case to assess any problems that may be written in the dust. Normally, the inside and outside vents will have dust accumulated on them. This should be regularly removed as dust build-up in the air vents can restrict air flow and lead to overheating. However, dust can also gather in a place that it shouldn't. Look over the case thoroughly for dust, corrosion, leaking battery acid and dead insects. Because you are working inside the case, you must use ESD protection and safeguards. Using a non-static vacuum cleaner is best as using compressed air can push dust onto components and cause problems. Check cables and wires for loose connections.
If required, the outside of the case should be cleaned with a dampened lint-free cloth, adding a mild detergent to the cloth to remove stubborn stains. Solvent cleaners are not recommended for plastic cases.
Any time you open a PC, perform a little preventive maintenance. If nothing else, vacuum the system case to remove all the dust that has accumulated inside since the last time it was cleaned.