If you are have issues getting Asp.net 2.0 membership and personalization running under Vista then you are not alone: there seems to be security issues dynamically creating the database.
Luckily the workaround is pretty straight forward, all you have to do is:
1. Install SQL Server 2005 Developer edition
2. Create a Database
3. Run the ASPNET_REGSQL utlity
4. Tell ASP.NET 2.0 to use this database with
<add name="LocalSqlServer" connectionString="Data Source=localhost;Initial Catalog=aspnet;Persist Security Info=True;User ID=sa;Password=Pwd;Pooling=False"/>
Luckily ScottGu has documented these steps at: