For the past several weeks now when I boot my MacBook Pro 15" i7 (only about 3 months old) the hard drive makes a grinding noise for about 3 seconds. It only happens on startup. It sounds to me like the hard drive head is moving all the way from one end of the hard drive platter to the other. I don't see any other issues and the laptop is otherwise silent. Is this something I need to worry about? P.S. I just rebooted again to see if it happens subsequently and it does. HOWEVER, I listened carefully and it sounds like it is coming straight from the DVD drive on the back right-side of the laptop. It sounds like the optical head is scanning for 2 seconds. Thanks.