Hi, I've been using a 12" Powerbook lately and I've noticed that every minute or so, I hear a slight whirring noise. It's not a "clicky" disk access noise but sort of sounds like a drive spinning up. It spins up for maybe 20 or 30 seconds and then stops and then does it again about a minute later. Is this normal? I've been using it in a very quiet room so I'm not sure if my regular Powerbook does this and I just don't notice it. It's not a loud noise so would be easy to miss I suppose. Thanks in advance for any help.