Strange, when the fans start running fast as it heats up in Windows, it feels like there's something loose inside the MacBook when I tilt it. But more noticeably, it 'coughs' out dust through the ventilation. Like, lots of dust. It happened to me twice in my 8 months of ownership. If I didn't know any better I would have thought it was some sort of advanced mechanism to clean the insides of dust. Can anyone tell me if there's anything to worry about? and why there seems to be something loose inside the computer only when it heats up?