[Marco van Herwaarden]

My advise is based on an integration of the vBulletin user system in your custom website application. This proofed the easiest and most flexible solution in most similar scenario's. To initially load your existing users into vBulletin, you would need to do a 1 time import.

1. Regstration of new users should go directly into the vBulletin. It is possible to create a registration from both the forums or your custom pages.

2. If the site is setup corretly, the cookie/session set by a login would work on both the forums and your custom pages.

PS Integrating the vBulletin framework into your custom pages is something that will require some PHP knowledge. In most situations this should however not be overcomplicated.