Take the side off and see how much dust is in your cpu fan and the other fans.
DON'T DO THAT!!
You'll kill all the dust-moles, and the scare the shyt out of the sheep!
Next thing you know, they'll all run into PSU for shelter, and you'll be smelling lambchops for months! Little popping sounds as they're disconnected atoms are blasted from the aluminum-cruicible that is their home!