I've got a brand spanking new 24" iMac, and I am experiencing more noise out of this thing than I expected... The noise started as a rythmic rattling in the back- I thought there was a lawnmower outside my window moving around, back and forth- it would rattle for a few seconds, then stop for a few seconds, then come back for a few seconds, then stop... etc. That has stopped (for the time being) only to be replaced by something quieter, but actually more annoying. Basically, now, it does a very low-pitched moan every few seconds, lasting for maybe 2 or 3 seconds, on and off, on and off... its so low pitched that you almost feel it as much as you hear it. Beyond that, however, I have one other concern- this thing is NEVER quiet. At all times, it sounds like the fan is running, constantly, with a low whooshing of air. This concerns me because Ive heard a lot of other people describe their new iMac as dead silent. Any ideas for me? Is this something I should be taking my system in for, or is the constant presence of a low whooshing noise just par for the course, with attendant throbbing?