go to here <A HREF="http://www.entechtaiwan.com/ " target="_new">http://www.entechtaiwan.com/ </A>, they offers program for overclocking videocards.
edit: the following is from a different post on another board. hope it help too.
Overclocking a video card is a bit easier than overclocking an entire system. You're going to need some kind of video card tweak program.
Although there exist tweak programs designed for specific video cards or series of cards, Power Strip by EnTech Taiwan works with many different types of video cards and would be a good place to start. If you like the program, why not register it to support the company?
When overclocking your video card, do so in small increments - most people suggest jumps of no more than 5MHz, which is as good a rule as any. With every increase in the speed of your video card's graphics core or memory, run a series of tests. Try A benchmark program such as 3D Mark 2001 or playing some levels in your favorite game.
If, after a bit, you don't experience any graphical artifacts - flashing polygons, "static" or "snow" effects on the screen, or anything else that you shouldn't be seeing - then increase the clock speed again. You can keep doing this until you reach the point where you start experiencing graphical errors. That's when you've gone too high. So back it down a bit and always be on the lookout for other graphical anomalies that might require you to lower the speed a bit.
About the only thing you can do to try and overclock further is to improve the cooling on your video card by putting some kind of third-party heatsink/fan unit on it. But even this might not guarantee a much higher overclock.
If you're experiencing graphical strangeness, don't mess around. Decrease the clock speed as soon as you can. Leaving the video card at settings too high can cause the chip to overheat, and many a card I've seen destroyed by running too hot.
<P ID="edit"><FONT SIZE=-1><EM>Edited by klau851979 on 08/25/02 04:11 PM.</EM></FONT></P>