Dust, dirt and pet hair can accumulate inside your desktop computer or laptop. Dust builds up on the fans and can cause them to slow down, get louder or stop completely. A brush is needed to loosen the dirt. Compressed or blown air can get the loosened dust off of the fans and out of the case. It's best to do this outside because of the amount of dust that comes out. Avoid using the air canisters you find from the store because they may contain combustible liquid.
Open the case and loosen the dirt from the fans with a brush.
Take the computer outside and spray the dirt away. Dust clouds can form when cleaning out dust from the computer. You won't want to do this indoors.
A thorough wipe down of the case tower or laptop will have computer looking like new again.