My drive has been doing this for prob a year now and progressively getting worse. I dont get any open tray errors or anything. It only does it when spinning down. Any ideas of what it could be? Sorry about that knocking sound i dont know what that was from i was holding my webcam. http://www.youtube.com/watch?v=wnDd4EeILBk&feature=channel_page
mine used to make noise when spinning down also, i just had to get used to it. never damaged anything Worst case, just get a new drive.