How to run programs in python2 and python3

You can specify the version in the executable name python2.6 and python3.

Instead of just typing "python" on the command line, use the full path the python.exe that you want to run: FULL_PATH_TO_PYTHON_2.6.6\python.exe or FULL_PATH_TO_PYTHON_3.1.3\python.exe should distinguish between the two.