Python 2.2.1 Windows / install variables ?

[Rich Pinder]

I've loaded the windows installer (Python 2.2.1 (#34, Apr  9 2002,
19:34:33)), have the PYTHONPATH variable set correctly, and have the
executable in the path.

I'm trying to load three add on's (4Suite, PyXML, and Interbase database
adapter).  

On the second install screen (on all three) it prompts you for 'which
python installation to use' - and there are no entries to select.

I'm assuming another environment variable is not correctly set - and I
can't find it in the readmes or the FAQ's.

Thanks in advance for any help you may have.

Rich