Computers are not invulnerable to dust. They have a tendancy to get clogged up with plenty of dust which at best causes overheating. It is a good idea to regularly clean out all the dust in a system to keep it as cool as possible since dust is an insulator. Removing the dust will allow better airflow, especially through fins on heatsinks and lighten fan blades, allowing them to turn faster.
Another tip to keeping a computer running in peak condition is to oil fans. Anything that moves should be well lubricated to allow it to do so smoothly and fans are no exception. Every once in a while (at least once a year, depending on how dusty your environment is) you should remove the fans in your system, take them apart, and oil them.
To oil a fan, you need to disassemble it. This is the tricky part. To disassemble a fan, you need to remove any stickers that cover the capstan. Next, remove the washer that holds the capstan. You will need a pointy knife or something to do this. Usually they will be made of plastic, but sometimes metal. They will almost always be a small flat disc with a hole in the middle and have a cut (think of a “C” where the ends meet but do not attach). Once this is off, you can remove the fan blade assembly. Before oiling it, you should thouroughly clean it. All kinds of grime and grit can get in there and cause it to make noise, as well as slow it down and create friction heat. Once you’ve cleaned it, then you can oil it. The type of oil does not matter too much depending on the fan. Most fans are cheap anyway so you do not need to shell out for top of the line lubricant. Even vegitable oil is better than nothing in a pinch. Synthetic teflon lubricant can be found in any bicycle shop and works great. You should oil the parts that touch and move. This includes the capstan, and the hole in which it goes. You will also want to oil the joint where the capstan attaches to the blade hub and where the blade hub rests on the washer. Do not over-oil since that will just make a mess with no extra benefit. In fact you should probably clean up any excess before putting it back. Put the blade assembly back into the fan and give it a test spin. Make sure that it is running smoothly. Now place the holding washer back on the end of the capstan and finally the sticker. Put the fan back, plug it in, power it up, and watch it spin. You may want to consider comparing fan rotation speeds before and after. Also, make sure to notice the noise level after oiling.