Vacuuming definately keeps dust down. Use a dust mask when if you're blowing, and it wouldn't hurt vacuuming if the dust still irritates you.

It does sound like this is an isolated incident so it might not be a problem with other computers. It could be because you're not used to it or because of the particular dust in the system. The thing about cleaning out other peoples computers is that you enver know what kind of allergents are floating around their house.

I'd suggest vacuuming if you have a shopvac with the right attatchments, and only blowing air of you have an air compressor, the cans are a waste of money and don't work very well.

Itdupuis is right about dust jamind if you blow it around, if you're going to blow, always blow away from the optical drives and use the compressed air to spin all the fans once the system is clean to make sure they're not jammed up.