Find:
Replace with:
in at least pubilc_topic_page.pl, maybe other files too.
Then make sure you've got a page, called
#.html, where # is the forum number, for every forum you've got. Those could be set up as simple redirector pages to automatically take you to the real page you want to go to (1.html --> blargh.html, for example), if that's the way you want it; but they'll need to have that filename, otherwise it won't work.
Hope this helps.
---Skorpion