Each summer we take every computer in the Distrct outside and blow the dust out with an air compressor. I've been asked from time to time why we go to all of this trouble, and the best answer I can give is that dust kills. In fact, in the PC world common, household dust accounts for more component failures than any other issue.
      You may be wondering at this point just why dust is such a big problem for electronics anyway, and the answer is twofold: it can cause a short circuit, and it can contribute to overheating. First off, dust can be electrically conductive, which means that if enough of it builds up on a board it can literally rewire the circuit, potentially causing a lot of damage. It's the second aspect, however, which is the more common, and the more destructive problem.
      Any electronic device creates heat as a byproduct of its operation, and modern computers are jam-packed with millions of microscopic electronic devices all working together at once. This clustering of various devices generates a lot of heat, as anyone who's been couped up in a lab full of computers with a faulty air-conditioner can attest. The typical computer today has three or four fans built into it to help move heat away from the sensitive electronics and out into the room. Dust in the fans causes them to work less efficiently, while dust accumulated on the circuitry (as shown in this picture of one of the computers at the Elementary campus) acts as a nice, warm blanket. This dust blanket prevents the heat from escaping into the air where it can be evacuated from the case.
      You can help prevent this on your computers at home by periodically using the hose attachment on your vacuum cleaner to suck dust out of the fan grates and other openings in the case. It's also a good idea to remove the case and blow the dust out once a year. You don't need an air compressor to do this, and in fact using a shop compressor without the proper filters that we use here at the school can do more harm than good, but you can buy cans of compressed gas at pretty much any office supply store for a few dollars. It's a small investment that can save you a lot of frustration in the future.