I just noticed a very low, almost imperceptible (but loud enough to make itself be known it's there), clicking noise on my new 20" alum iMac (for more specs read my sig). It is a constant noise that will not change in intensity (it is on all the time, starts as soon as I turn on the machine, stays on all the time and will not get any louder or quieter, until I shut down the machine). All this makes me think it must not be the HD, unless it's spinning all the time...which I seriously doubt. Maybe it's the fan, but that will mean the fan is stuck and working full time, never stopping. In which case, how can I tell when the fan is on? Unless the fan is on all the time on both of my iMac's, I can't seriously hear when they go on and off...as they probably should according to CPU temp (then again, how can you tell what the temp is?...I've read some posts in which they state the exact working temp???). I hope this is not a serious problem, because even though I can take my computer in to be replaced or fixed with the authorized dealer (remember it is still under warranty), it does take weeks to get it back...I replaced the mighty mouse on my 17" iMac and it took 3 weeks!!! TIA for any help/guidance.