Hi and thank you for all the good advice. I had cleaned out the dust bunnies with canned air about 4-6 months ago....but....wow! This poor computer was gagging for air! I'm surprised it was even running, it had so much dust. I did move it to this new location in the office after the last cleaning, so I think that is a pretty obvious clue that I need to move it to a better spot. Anyway, back to the problem. It is the power supply fan that is making the noise. I'm not happy about that since this model uses an expensive power supply. I cleaned it thoroughly with a brush and a vaccum, but the noise continues. I would prefer to leave the computer on all the time (or at least until I feel I need a reboot), but do I have too much of a fire hazard at this point? Should I just wait until it dies, replace, THEN continue leaving it on if I choose? Thanks again. I cannot tell you how much I have come to rely on all the info from this forum. Linda Denny The NOSPIN Group Promotions is now offering Mandrake Linux or Red Hat Linux CD sets along with the OpenOffice CD... at a great price!!! http://freepctech.com/goodies/promotions.shtml