Currently, when you use an MSI installer (and possibly also EXE) for a Python module, it automatically detects the location of your various system's Python installations. This is very convenient.

However, this can be a problem sometimes, if your Python installation doesn't conform to what's required by the installer. For example, if you want to install the module in a virtualenv:

http://serverfault.com/questions/305008/installing-compiled-python-modules-on-windows-on-a-virtual-env

The installer doesn't give you any option to manually enter a path of a Python installation, so you just can't install!

The installer's automatic Python-finding mechanism should degrade gracefully; it should offer to automatically find your Python installation, but it should allow you to bypass it and type it in yourself.