Just found this nifty little program which has solved a lot of hassle for me! My 6600gt was really load and 100% fan all the time even in 2d. But now, I have found something which allows me the change the fan speed in 2d and 3d mode.
Here is the link: http://www.gainward.com/html/downloa.../expertool.htm

Now 6600gt is now wisper quiet in 2d mode and less loud than it was before in 3d mode.
55% fan in 2d and 98% fan in 3d (that 2 from 100% and 98% makes a huge difference to the pitch of the fan)
I think it works with 6800 series and my temps havent risen much from before. Im now 60 degress in 2d and 82 degrees in 3d, as opposed to 56 degrees 2d and 80 degreees in 3d. Check it out, i recommend. John