Another program that does more then what you could hope, (although very dangerous and much like garhar I disagree with doing it all together) is called rivatuner. That program will do everything you need it to do and more, but be aware, over-clocking any piece of hardware voids it's warranty and risks destroying it, so use the highest caution possible.
The Guru of 3D Download Section << Link to the program download. Good luck!