My PB, the 15" 1.67 hi res model, currently in disarray with the battery not charging, has had it's ups and downs over the years. But one thing I've noticed since I got it in late 2007 is the fact that I can only hear one fan spinning up in times of hotness. However when I first pulled the thing apart to repair something in it, I discovered it actually has two fans. The one on the left (left as in as you look at the keyboard) definitely spins up and makes that signature whirring sound, but I don't think I've ever heard the one on the right making any noise at all. I've even stuck my ear to the vent on the back of the powerbook when it's been running hot and, while I can hear airflow from the left hand fan I can't from the right. That's not to say the right hand fan isn't running at all of course, it could just be whisper quiet and the one on the left is the only one that ever gets powered right up to make that noise (the case does always seem to get a bit hotter on the left than it does the right). I do wonder though if I've got a dud fan in it. Has anyone else here who has one of these PB's ever noticed this same thing or can they can definitely hear both fans powered up when the system get's hot? If I end up having to fix my DC board to rectify my battery charging issues I figure I might as well fix that fan too if it truly is broken, it might make the system cooler in future and thus make components like the DC board and the Mac overall last me a lot longer.