Firstly, the recent versions of MediaWiki won't work as the depend on PHP5, which we haven't got yet! So the most recent version is 1.6.10 which at the time of writing was available here
Untar this as normal and create your virtual folder. MediaWiki needs PHP session support so uncomment this in your php.ini (if you haven't done so already) and restart Apache.
Now normally at this stage you would just start the installer but, believe me, it won't work.
The first issue is that relative paths seem a bit broken so to correct this, edit the file /config/index.php and change all the instances of ../maintenance to /wwwroot/wiki/maintenance substituting in your absolute path.
Gotcha! Don't use logical names with dollar ($) signs as PHP interprets these as variable names.The next problem is that the table building script uses quotation marks when defining ENUM values. I'm not sure if this is a specific issue with the VMS version of MySQL but the interpreter doesn't like these. To fix this, edit the file /maintenance/tables.sql and search for ENUM. Change all quotes in these lines to apostrophes (').
Now, you should be able to start the installer, http://myserver/wiki/config/
Depending on your security settings the installer may not be able to write the config file itself. If so, copy and paste the text it provides into a file called LocalSettings.php and save it to the root of the wiki virtual folder.
That should be it. Roll on PHP5!
