get nvmax from www.nvmax.com that will do it for ya.

Hercules has a tweaker to overclock their cards, and that should be on the cd. If not you can get it off their website.
Ive got mine overclocked to 221 core and 210 ram. You will see some heavy artifacting in 3dmark2001 with this high of overclock on the ram. And just be sure youve got some cooling on the core. I have a dual fan blowing onto some of my addon cards, and so far no problems. You can clock the ram higher that 210, but the artifacting becomes extremely obvious and annoying at this point, so its your call.

I know everybody is overclocking and I know it works well for many people,but I must throw in the fact that things can begin to break and burn-up as you start running things out of factory specs.
I have personally burned up lots of things screwing around, including cards and motherboards. Goodluck, but don't be surprised if your curiosity gets the best of you.Not a flame, just some good sense.

I have found a reg entry called coolbits that works great for me. Allows overclocking just fine up to 220/195 throught the Display Settings.
 
I can email it if you want.
 
edmarvin@hotmail.com