Perform a fresh install with a freshly made database to test your customizations on. Then you will be sure that whatever changes you've made are the result of you, and not something that has happened beyond your control -- such as a user or live forum script/advertisement. You will need to create some test categories, forums, and posts to work with.
Be aware, that columns are affected also by the user settings. ie; all-on/all-off, left-only/right-only, show profile-details-on-left for profile editor, hide columns for registration settings, ignore shoutbox in column for shoutchat page, and several other locations. There are template column controls in the libraries files which also need to be updated.
