What is it?
NVIDIA nTune Library is part of NVIDIA System Tools (nTune), a collection of utilities for accessing, monitoring, and adjusting system components, including temperature and voltages with user-friendly control panels within Windows, rather than through the BIOS. System Tools has a feature that automatically adjusts settings and tests them to find what it believes to be the optimal combination of settings for a particular computer hardware configuration.
Description of ntuneserviceenu.dll from NVIDIA
“Enables one of the safest and easiest ways to automatically optimize your PC. nTune automatically detects the application running and dynamically optimizes the PC settings. Faster than tuning by hand, nTune delivers optimal settings for bus speeds, HyperTransport, memory timings, CPU registers, fans, and voltages in a safe, easy-to-use Windows interface. Provides the ability to overclock system settings without entering the BIOS or changing hardware jumpers.”