I have a website which has its user management. That mean I have a table in a database to store users' accounts. Then I want to build a forum in such a way that users don't have to register again. So what should I do: 1) The forum and the website use the same user table in one database? 2) The forum and the website use different database but with the same user id? And which of the forum should I use? I know that vBulletin is a powerful one, but is it flexible enough or easy enough to do that? Or should I use phpbb which less features? Thanks in advance!