You dont need to make these things, there are plenty of free ones available. All you need to do is find somewhere to load up and host the SQL database required to do so.
If thats beyond you there are actually some very good free
and hosted forums. The only thing with these that a LOT of people moan about and for no really good reason is that they have advertisments on them.
http://forums.asp-dev.co.uk/
http://www.akheva.com/
http://www.proboards.com/index.html
http://www.instantmessageboards.com/
four picked at random from a google search. I used to have a proboards forum on a project I abandoned and it was fine. Adverts popped up every third or fourth refresh but if the content of the forum is good no one gives a monkeys.