why not use one of the free offerings like the personal version of community server?

http://www.communityserver.org

dont think theres much point in recreating the wheel on this one, unless it's a commercial project and you will be funded to develop a new forum module thers other ones like bbForum however that requires php and mysql whereas community server is asp.net and sql server

If your site is commercial then you would need a commercial license for community server. I am not suggesting that you develop something yourselves using community server as a guide, I am suggesting that sometimes the cost of development time will surpass the cost of a license. Or in a scenario where a forum is on your wish list but other projects or tasks are a priority, then with a small installation overhead you can have a fully functional forum for a reasonable price. As in actual fact a Forum mechanism while simple as an idea can be quite a complex task to accomplish. If you want to play with something a little buggy and unsupported, why not look at aspnetforums (if you can still get hold of it) that was what Community Server originally was before it became a commercial project. You will see very quickly from that just how much work would be involved in making one yourself