Multiple Versions of Python on Windows XP

[Colin J. Williams]

Could anyone please point me to 
documentation on the way the msi 
installer handles multiple versions eg. 
Python 2.5, 2.6 and 3.0?

What changes are made to the registry?

Is there some way to specify a default 
version in such a way that it can be 
changed as necessary?

PyScripter uses an option to select a 
version eg.

C:\Program 
Files\PyScripter\PyScripter.exe --python26

but I'm having some trouble with it when 
I attempt edit a python file from the 
Windows Explorer.

I would appreciate any information.

Colin W.