Hi All, I recently added a 27" i5 late 2009 model to my home. I have a 2010 21.5 i3 model that is very quiet. When I set up the 27" (refurb store purchase) the other day, I noticed the hard drive making (not as loud as a PC) ticking noise behind the machine. I called apple care and went thru a couple things, then instructed me to take it to the store for a look. The gentleman at the Genius bar ran thru some HD tests and updated the software. He said everything was fine, but it was noisy in the store to see if we could hear the HD running. When I got home, I can still hear that slight HD noise when it is quiet in the room. He said that some of the HD's make a slight noise. My 21.5 never made a noise so I was wonder if this was normal or not? Thanks for any input.