SETTING THE PATH ENVIRONMENT VARIABLE (WINDOWS ONLY)
The PATH environment variable specifies a list of directories that are searched whenever you specify an executable program from the command line. A very good guide to setting up your environment so that the Python executable is always available in every command shell is to follow the instructions here:
http://www.blog.pythonlibrary.org/2011/11/24/python-101-setting-up-python-on-windows/