Spre ,download a overclocking Utilities program from here
click here this allows you to overclock your card, make sure you use standard Nvidia reference drivers.Note it`s under the utilities section & for Win95/98.
Also I believe(not sure on this)that the Hercules software allows overclocking from its software so just move the slide bar to a faster memory/ram setting for overclocking,if you don`t have this just install the above software ,but make sure you uninstall the hercules drivers/software before you install Nvidia drivers etc.