The official OpenCV2.2 installer does not install the Python bindings into your Python directory. There should be a Python2.7 directory inside your OpenCV 2.2.0 installation directory. Copy the whole Lib folder from OpenCV\Python2.7\ to C:\Python27\. Then set the windows environmental variable PATH to include your OpenCV\bin directory together with C:\Python.
Alternatively use the opencv-python installers at http://www.lfd.uci.edu/~gohlke/pythonlibs/#opencv.