phpBB click here is about my all time favourite.
It's drop dead easy to instal and configure and works like a charm.
Without the full details of your web server account it's a little difficult to say without any doubt that it will be all you need, but take a look and if it isn't suitable post again since there are some other alternatives.
I'll mirror this answer in your other thread to make sure you see it.
Oh, and depending on how adventurous you feel, you can always write your own discussion board...