I have two python installations, 2.5 and 2.6 I want to change the default python interpreter from 2.5 to 2.6. Anyone know how?
PYTHONPATH is NOT what you are looking for. That is for varying where Python's "import" looks for packages and modules.
You need to change the PATH variable in your environment so that it contains e.g. "....;c:\python26;...." instead of "....;c:\python25;....". Click on start > control panel > system > advanced > environment variables. Select "path". Edit it. Click on OK enough times to get out of there.