ASP.NET configuration issue, switch to use SQL Server 2008

I would like to configure my asp.net application to use an SQL 2008 Server database rather than the SQL express, which is the default I think.
 
I have found this file C:\Windows\Microsoft.NET\Framework\v2.0.50727\Aspnet_regsql.exe which has allowed me to add a database to my sql 2008 instance. I'm guessing now I need to edit my web.config file to use this database. Here is my code;
 
<?xml version="1.0"?> <configuration> <connectionStrings> <add name="ApplicationServices" connectionString="data source=localhost;Initial Catalog=aspnetdb;Integrated Security=True; Instance=true" providerName="System.Data.SqlClient" /> <add name="MAINDBConnectionString" connectionString="Data Source=localhost;Initial Catalog=MAINDB;Integrated Security=True" providerName="System.Data.SqlClient" /> <add name="MAINDBConnectionString2" connectionString="Data Source=localh ...