When it comes to the HTML design, you certainly can use Dreamweaver.
However, you'll also need a server side programming language like ASP.NET, ASP, PHP etc to create the functionality of a site like this: e.g. Users, Threads, Replies etc coming from the database. DW is not good at ASP.NET but has reasonable support for ASP and PHP.
Finally, you'll need a graphics program like Fireworks or PhotoShop (Adobe), Paint .NET (open source) or Paint Shop Pro (Corel) to create images.
You may want to take a look at the book Beginning Dreamweaver MX 2004 as it helps you get started building sites like this: http://www.wrox.com/WileyCDA/WroxTit...764555243.html
Hope this helps,