Re: Forum's permissions
There are multiple ways to assign permissions. My description above was for the Registered group's global permissions, but there are two other ways the Registered group could be getting the "Can admin forums" authority. The forum could have object permissions granted, or the forum could be in a category that has permissions granted.
First check the Forum object permissions. In the menu click on "Admin Forums" link which is under "Forums". The rows of forum names will have icons at the far right, one of which is a key. If the key is green, then permissions, which override the global permissions, have been granted. Click on the key and then make sure the "Can admin forums" permission is not checked for the Registered group.
If the problem permission was not checked for the forum object, then the permission may be coming through the forum's category permissions. Forums may be in more than one category, so first check to see which category or categories the forum is in. In the list of forums you get from clicking on "Admin Forums" link in the menu, click on the "edit" icon for the forum. Part of the way down the forum edit page is "Categorize", if the categories are not listed to the right, click on the "Select Categories" button, and then make note of which categories are selected.
Next, click on "Categories" link under "Admin" in the menu. On the Categories page click on the "Admin Category" tab at the top. This will list the categories, there will be a key icon for each category. If the key is green, then that category has permissions assigned which override the global permissions. Click on the key for the category, or categories, that the forum is categorized as and again make sure the "Can admin forums" is not checked for the Registered group.
In each of those places, you may also want to decide about the "Can edit own forum posts" permission too.
Tom