OK, So i've just added an external HD for time machine and the spin up noise drives me nuts every 1 hour. I've moved the disk to somewhere where its at least a little better but anyway I was wondering whether to disable the "put hard discs to sleep when possible" ? tab to stop it spinning down (and hence stop the spin up noise since it'll always be spinning). I can't really hear the disk while its spinning! I guess unticking that might also improve response in general since the internal iMac disk will also NOT spin down. And here is where my worry is. If I disable the "put the hard discs to sleep when possible" the internal disk will be running constantly. Will this cause unnecessary heat to build up in my iMac? How many other people disable the disk sleep?