what is the correct way to remove a phpbb forum ? i've tried deleting the directory but then when i add it again it lists a number of "existing non-existing" forums that point to the same one.

delete the folder, then the database.. did you remove the database?

yes. and when i create another fresh forum a list of previous forums come up pointing to the same structure. its not a big problem other than having extraneous data in the control panel.