About compressed air - I heard that the force of it can damage some sensitive chips or something - dunno, but at least be a bit wary of it.

...wow, that's a lot of dust.
I've got a 1996-7 Pentium 200MHz computer right behind me which hasn't been cleaned out for years, and I don't think it's that bad (but then, Pentium I's never really heated up much, so never really needed much cooling).