How to install phpBB inside gallery

I get the feeling that I'm going the opposite way compaired to alot of people.

I have an existing install of gallery 1.51, and was hoping to add a phpBB forum (or any type of forum I suppose) to that install. I know that you can go the other way, and install gallery into phpBB, but is there a way to keep my main page as the gallery, and have a forum in a sub folder?

Thank you!
Terry