SharePoint 2007 and MOSS 2007 are built on ASP.Net 2.0 which means they can leverage many of the same features of ASP.Net 2.0 including the AspNetSqlMembershipProvider for use with Forms Based Authentication. There are great guides to configuing FBA: Andrew Connell had the best article first.
When we Creating Two Web Applications, One For Each Authentication Mechanism on same port(As 80) then you have to add host headers from which the application will be browsed. But the when you create the web application with host headers(as extranet or internet) then the URL does not resolved. It will does not display your site. To resolve this you have add DNS entry for that and also configure AAM for the same.
When we create site collection and above all settings done, then it prompts for the login. But after giving credentials it again and again prompts for the credentials and we cannot browse over site.
After goggling on this issue I have found solution of this issue at one link.
At above all the configuration steps I think It would help you in configuring FBA on SharePoint 2007.