you have to create a custom fan profile to change the fan speed manually. There is a big 4850 thread that one of our regulars started a couple months ago that has all the details. I couldn't find the thread when I searched for it originally so I just did a google search and found a thread on another forum that showed how to do it. It was kind of a pita for me, took me several hours to get it right, but now my fan runs constantly at 37% and the card stays at a cool 50c.