The command used for adding asp.net 2.0 membership stuff is
aspnet_regsql -A all
-C "Data Source=.\EXPRESS;Integrated Security=True;User Instance=True"
Adds support for one or more ASP.NET application services. Service identifiers can be specified together or separately. The following identifiers are used for ASP.NET application services:
all - All services, including common tables and stored procedures shared by the services
m - Membership
r - Role Manager
p - Profile
c - Web Parts Personalization
w - Web Events
-C - Specifies the connection string to the computer running SQL Server where the database will be installed, or is already installed. This option is not necessary if you specify only the server (-S) and login (-U and -P, or -E) information.