Building a forum as good as phpBB would be hard. Im currently making my own forum from a guestbook script which was just a 'add info to database' and 'read info from database'. Put them together and im starting to learn new things. IOn the other hand i still will be thanking
markl999 (I think thats his name...

), he helped me with a lot of mysql database problems.
So before you make a forum, learn basic things and make your own scripts that can be built up to a forum. Like Guestbook, News Script, User Authedentification (sp?)
=D Dale