Separate Windows versions of Python

[OldGrantonian]

I use Windows Vista Home Premium. I have Python 2.6 currently
installed. I'm not a techy.

I want to use "virtualenv". When I try to install the latest version
of virtualenv for Windows, I get the message that Python 2.5 is not
found.

How do I install Python 2.5 (or anything else except 2.6) so that I
use the correct version of Python at the correct time.

For example, do I need to edit the "path" variable each time that I
want to change versions from 2.5 to 2.6?

 

[OldGrantonian]

Many thanks for the very detailed answer

I will go ahead right now and implement all your suggestions.

 

[Terry Reedy]

On windows, major versions (..., 2.5, 2.6, 2.7, ...., 3.0, 3.1, ...)
can coexist quite successfully. Find and run an installer for the
latest version of 2.5 (2.5.4, I believe) on the Python download page.
That will make 2.5 your default Python.

believe the installer gives one the choice as to whether or not to
make the new installation the default -- which is to say, the one
registered with .py, etc, extensions.