How do you clean the inside of the computer?

You can clean a computer inside and outside without problems with some basic care. You need to protect it from static and and any thing which can short circuit any part of the electronics when you turn it on again. To dissipate static from your body, You need to ground yourself touch a metal part regularly or use a anti-static wrist pad connected to ground/metal body of the computer. You can separate cables etc from parts (you should have knowledge on how and where to put back all the connections). clean parts with a cotton cloth (may use a PCB cleaner) and or a compressed gas container to blow away all the dust. Clean the vent fans and filters which tend to gather a lot of dust. Cleaning the heat sinks also helps cool down the chips better than if covered with dust. Make sure every thing is dry and no connections loose and no unwanted metal parts inside the computer when you close it.

Use a hair drier carefully.