I still don't get the point. The mySQL database actually IS the standard one in use by the WebWiz forum, it's only filled with text and numbers coming from another database by an automated .asp script. People could write the same things from their keyboards, only the way they're written there changes.
What if we lock all the threads coming from the old forum after the conversion? Would that fix these hypothetic issues? After all we don't need to have all those old topics still active, we'd just like to have them available as a memory of past discussions in the same place.
The reason why we don't go to SQL server as you suggest is obviously because the hosting is much more expensive and we will never be able to afford it.