For a good while, I have had problems with the fan running on my late 2006 macbook. The fan will simply run, seemingly forever even when not under a load. I expect it to run when doing intensive work, etc., but it runs even when just reading email and nothing running in the background. I have tried all the suggested fixes -- SMC, PRAM, permissions, etc., but nothing has helped. I even took it in to have the tech look at it while it was still under warranty. He said he could not reproduce (can't understand that -- all I have to do is open iPhoto and the fan will start). We have cleaned the fan, etc. all to no avail. Activity Monitor shows nothing unusual, and the computer does not get excessively hot only warm. Now the crux of the story! For some reason I decided to take the battery out of the computer and run only on electric. No fan noise! I fired up several videos at the same time, started surfing the web, had lots of things open -- all with no fan running! To check another angle, I put the battery back in, but unplugged the electric. Got a "little" fan noise, but not nearly like I had been getting. So -- question is -- what is going on here? I have always left the battery in place and I keep it plugged in to the electric. Should be fine. But maybe there is a reason the fan does not run when one or the other is missing? Would love for someone to explain what is going on here and why I am getting the behavior I am getting. Thanks for any and all input!