Quick solution: set PYTHONHOME and PYTHONPATH and include PYTHONHOME on PATH
For example if you installed to c:\Python27
set PYTHONHOME=c:\Python27
set PYTHONPATH=c:\Python27\Lib
set PATH=%PYTHONHOME%;%PATH%
Make sure you don't have a trailing '\' on the PYTHON* vars, this seems to break it aswel.