As a major computer repair shop in the Portland area, we see all sorts of machines. A common issue with some is that they are just down-right filthy. Systems that are covered hard drive to motherboard in a layer of dust or tobacco crud. These systems often have fans that have stopped working, which lead to overheating and electronic component failure. Here's an example of a system that was brought in for a number of issues, and had to use our System cleaning service:

So What Can I do About it?

If your computer hasn't been cleaned in a long while, it's best to unplug the whole system, and take it outdoors. Remove the case enclosure (usually the left-side comes off with two screws in the back), and, using a can of compressed air, or a full blown air-compressor, blow out all of the dust. Make sure to get in-between devices and fan blades, you'll be amazed how much dust can accumulate.

Before powering up, make sure all the cables are still attached properly and that nothing was jostled loose during your cleaning. Close up the case and power it on! Your computer will thank you by not failing early and continuing to run for years and years.