Took a can of air to my 800 here. *Hack* *hack* *Cough*
It's Hiroshima all over again...
One thing I also recommend is take the cover off the PSU (if you don't care about warrenties) and (Careful not to fry yourself) blow the dust out of it.
Around my area, it is really dusty. I guess I should start using my shop air compressor...