I currently have a HD Radeon 3850 manufactured by Triplex. I don't actually want to overclock my card (i felt this was the most appropiate forum though), but the heatsink fan is rather noisy. It doesen't have the stock heatsink fan most of the cards have. I read somewhere the fan speed can changed so that it runs slower in 2D applications and faster in 3D ones. Does anyone know how i would go about doing this, and what sort of temperatures should the GPU be. I have never done this sort of thing before.
Any help would be appreciated.

Download Rivatuner, this should allow you to change your fan speeds manually. There's also many guides out there that allows you to configure the fan so it runs faster automatically at a given temp.