Multiple Versions of Python on Windows XP

["Martin v. Löwis"]

>>> What changes are made to the registry?
>>
>> For a complete list, see Tools/msi/msi.py in the source tree.
> 
> I have scanned the file:
> http://svn.python.org/projects/python/branches/py3k/Tools/msi/msi.py
> 
> I don't find anything that addresses this issue.

Read the add_registry function. You may need to first understand
how the Registry table in an MSI file works.

> I am seeking some mechanism such that any of Python 2.5, Python 2.6 or
> Python 2.6 can be chosen as the currently active version.

If Glenn Lindermann's answer doesn't help, you need to explain:
what is a "currently active version"? How is one Python version
more active than any other?

> I was hoping that there is some simpler way than the "Repair" procedure.

See Glenn Lindermann's answer.

>> It would be good to be more specific with such statements: what troubles
>> specifically? If I play dumb, I'd say "of course - windows explorer
>> doesn't support editing Python files; you need a text editor".
> 
> Yes, I should have been clearer.  The PyScripter application locks up
> and must be killed, using the Task Manager.

I think you need to report that to the PyScripter authors as a bug.
I can't imagine how the "currently active version" can affect what
PyScripter does.

Regards,
Martin