If you're looking to tweak up your video card beyond the limits of what the official drivers allow you to do via their control panels, you cant look past RivaTuner. Guru3D have just made mention of a new and improved build (v2.0 RC 16.2) which brings full support for owners of GeForce 8800 series cards as well as support for the ForceWare 97.xx and Catalyst 6.11 driver suites.
RivaTuner is the most powerful tweaking utility for NVIDIA and ATI display adapters running under Windows 98 / Windows 98 SE / Windows ME / Windows 2000 and Windows XP. The purpose of this utility is to give you access to all the undocumented features of Detonator and Catalyst drivers. Drivers have a lot of undocumented registry entries. Some of them don't affect anything, but there are some that are very useful. In general, they cannot give you big performance boost but they can improve image quality and solve some compatibility problems. RivaTuner will help you to change all undocumented registry entries. It supports all versions of Detonators (now called ForceWare) drivers under Windows 98 / Windows 98 SE / Windows ME (Detonator 5.08 or higher under Windows 2000 / Windows XP).