Hi,
I downloaded CUDA 8.0 RC from following location for Windows 8.1 Machine:
https://developer.nvidia.com/cuda-release-candidate-download
While installing it fails half way and many of the component remains un-installed.
I have VS2013 and VS2015 Update 2 installed on this Windows 8.1 machine.
However, CUDA Toolkit 7.5 installs and works well on the same machine.