Just thought I would share...A couple of days ago my 1TB HDD failed on my late 2009 21.5" iMac. It was still allowing me to work, but was showing "Failing" in the disc utility. What called my attention to it was the much noticed noise the drive was making. This started a couple of weeks ago and was only getting worse. It sounded as though the drive was constanlty writing or docking. I was also getting quite a few "spinning beachballs" while doing no more than web surfing, email, etc.... Anyway, it is at a local authorized and recommended Apple repair shop getting a new HDD so hopefully I will be back up and running soon. Fingers crossed that my Time Machine back up from the external HDD will go smooth!!