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#11
I hope your not sticking the vacuum cleaner near any of your internal hardware... many a computer has been completely screwed because the owner has hit the motherboard with the nozzle of their Hoover.
As for Cleaning, I just use our air compressor (canned air would work just as well) to blast the dust out of the fans and the dust filters over the intakes, the rest of the case stays reasonably clean, although I'll give it a once over with a damp Chux cloth once in a while to remove any dirt and fingerprints on the outside.