Thought I would post this regarding the HD noise, since I think it may help other users. My iMac has the Seagate ST31000528ASQ My first 27, I restored completely from Time Machine, in other words everything (users, applications, settings, etc). The sound was terrible. So I got another 27 after Apple ran some Hardware tests and said it was a hardware, not software, problem. The tech seemed to think it was the fans. So I receive my replacement, same Seagate HD, 1 TB, etc. (Requested a WD drive but was told it was impossible) Restored completely from Time Machine again. Clicking was driving me nuts again. Talked to Apple, they told me to try and wipe the HD, start fresh, don't restore anything. I did. The HD was still way too loud (my 24 was silent), and distracting but the clicking problem reduced drastically. Apple told me I could restore back my files, just not the "settings" portion of the backup. (Side question - What settings do you actually lose by not restoring this? All of my 3rd party apps seem to be working as I left them, everything is the same in the menubar. Is it just a couple of the system preferences?) So I restored everything minus the settings. As soon as I booted back up and got on the Internet, the clicking started again and hasn't stopped since. It seems to have something to do with the TM backup, at least in my case. Or maybe the backup somehow conflicts with the drive in some way, or vise versa? This of course, is very disturbing, because I need to restore these files. I know in the Clicking thread some users had said that it didn't make sense for this to happen. But I can now vouch for this...and I felt it deserved it's own thread. Receiving a 2TB upgrade from Apple because of these problems, just hoping it works.