Why should you have your computer cleaned?

I have worked on many computers that stopped operating due only to the huge amount of dirt within them.  In at least 5 separate occasions, I was presented with a totally dead non-working computer that started working again after removing piles of dirt from inside of it.  Its very probable that many of the permanently dead systems where I found huge amounts of dust were ruined because of it.  To illustrate my point, have a look at some pictures here of what can happen to your computer if you keep it on a bare floor or in a dirty environment.

Computers from some of my clients.

Inside of the power supply

Actual SPIDERS living between the ram chips!!