NVAPI Reference Documentation
Release 435: August 22
Make sure you have the following files:
Operating System and Platforms
The current version of NvAPI is supported on Windows XP, Windows Vista and later, both 32-bit and 64-bit architectures. Some API calls are OS specific–see the individual calls for OS support information.
NVIDIA Graphics Driver Version
NvAPI is supported on ForceWare driver versions 81.20 and up. See the individual calls for specific driver version information.