Dan Attis has two great articles about configuring forms authentication against SQL Server with MOSS.
Part one - Configuring Forms Authentication with SharePoint
http://devcow.com/blogs/jdattis/archive/2007/02/23/Office_SharePoint_Server_2007_Forms_Based_Authentication_FBA_Walkthrough_Part_1.aspx
Part two - Configuring Forms Authentication with MySites
http://devcow.com/blogs/jdattis/archive/
Read the complete post at http://dhunter-thinkingoutaloud.blogspot.com/2007/08/sharepoint-2007-forms-authentication.html