Numpy installation through pypi (the default package index used by pip) generally fails on Windows computers. The easiest way to install on Windows is by using precompiled binaries.
One source for precompiled wheels of many packages is Christopher Gohkle's site. Choose a version according to your Python version and system. An example for Python 3.5 on a 64 bit system:
pip install C:\path_to_download\numpy-1.11.1+mkl-cp35-cp35m-win_amd64.whl
If you don't want to mess around with single packages, you can use the Winpython distribution which bundles most packages together and provides a confined environment to work with. Similarly, the Anaconda Python distrubution comes pre-installed with numpy and numerous other common packages.
conda install numpy