Do you have the option to overclock? im not sure if you have to run a patch to make it show up, But i think it may be visible with the Nvidia 42.01 or 41.09 drivers.
You can just use that > under desktop properties (display properties > settings > advanced > Geforce 4 (or whatever your card was again) > clock frequencies (depending on drivers the tab folds out or you have to click advanced again or something similar)
you can mess with this to your hearts content, and thats all you need to do, it changes your memory clock and core clock, you dont need to change anything in your bios.
adjust both by little increments, 10%, 12%, and so on if you like.
i did about 12% on my old GF2MX400 and it worked fine.
you can also download http://www.guru3d.com/nvhardpage/ this software which will tweak hidden features on your card and other nvidia cards this will also open up the clock frequencies tab from the above mentioned display properties, along with some others (i might have used this first to open the overclocking tab)
http://www.guru3d.com/overclocking.shtml this might help with other tips too, incase i missed any.
-- 09