[pmwiki-users] Problems using index.php

[Simon]

I have the following directory structure
(for a private PmWiki for a project)

/public_html/co/pmwiki/

pmwiki.php exists in the pmwiki directory

I only have access to /co/
I want to be able to have users enter http://example.co.nz/co
so I created index.php

<?php include('pmwiki/pmwiki.php');


When I enter the above URL PmWiki displays,
but it does not appear to calculate the correct paths to its directories,
especially /local/, do it can't pick up any of its parameters

you can see this here http://pmi.org.nz/conferenceorganisation/

I would appreciate any help on configuring this to work.
The platform is Windows and IIS

thanks

Simon