well, i would need to isolate my computer from my house, bringing all air to my computer from the outside. just picture a computer case
made of dust. that is my machine before i think 'i should really blow it out'.
then there is the story of my vid card. i had an 6800GS for a year, and didn't clean it. when i opened it for the first time, the heatsink was black dust encrusted (you know the darker kind on the dinosaurs in your basement, that is very sticky and smears everywhere) so i decided to bring my step dad's
industrial air compressor and blow the "c**p" out of it. well at 120 PSI it really ripped the dust off. i only hit the heatsink for like two seconds, but when put it back in my computer, i had no green output, the screen was magenta

oh well, i RMA'ed it and got a 7600GT for my bro hope no one here works for XFX

in hindsight it was pretty stupid but i learned that cleaning your card frequently is better than destroying it