compiling OpenCV 2.3.1 with CUDA 4.0

Accelerated Computing CUDA CUDA Programming and Performance
1

I actually installed: CUDA 4.0, Cmake 2.8.2 and i downloaded 2.3.1 version of opencv. But at configuring in Cmake, it give me some errors like this:

CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
CUDA_npp_LIBRARY (ADVANCED)
    linked by target "opencv_gpu" in directory C:/OpenCV-2.3.1/opencv/modules/gpu

despite it detect cuda but it does not configure.
thanks