I am trying to install DNN on my local machine. I already installed Visual Web Developer 2008 Express with MS SQL 2005 Express and the DNN Starter Kit which all worked fine. I can deploy the application and the installation script of DNN starts. The first steps work fine (select installation type, language, file permissions) while the next step where the database connection has to be configured, testing the connection fails with the following error:

Connection Error(s):
Index #: 0
Source: .Net SqlClient Data Provider
Class: 20
Number: -1
Message: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

I already tried to change .\SQLEXPRESS to .\\SQLEXPRESS (adding a slash more) but it does not work; changing it to DOMAIN\USER\SQLEXPRESS returns an error:

System.ArgumentException: Invalid value for key 'attachdbfilename'. at System.Data.SqlClient.SqlConnectionString.VerifyLocalHostAndFixup(String& host, Boolean enforceLocalHost, Boolean fixup) at System.Data.SqlClient.SqlConnectionString..ctor(String connectionString) at System.Data.SqlClient.SqlConnectionFactory.CreateConnectionOptions(String connectionString, DbConnectionOptions previous) at System.Data.ProviderBase.DbConnectionFactory.GetConnectionPoolGroup(String connectionString, DbConnectionPoolGroupOptions poolOptions, DbConnectionOptions& userConnectionOptions) at System.Data.SqlClient.SqlConnection.ConnectionString_Set(String value) at System.Data.SqlClient.SqlConnection.set_ConnectionString(String value) at System.Data.SqlClient.SqlConnection..ctor(String connectionString) at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters) at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(String connectionString, CommandType commandType, String commandText) at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(String connectionString, String spName, Object[] parameterValues) at DotNetNuke.Data.SqlDataProvider.TestDatabaseConnection(DbConnectionStringBuilder builder, String Owner, String Qualifier) at DotNetNuke.Services.Install.InstallWizard.TestDatabaseConnection() at DotNetNuke.Services.Install.InstallWizard.wizInstall_CustomButtonClick(Object sender, EventArgs e) at System.Web.UI.WebControls.LinkButton.OnClick(EventArgs e) at System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Using the "auto install" option (first screen of installation wirzard) produces the following error:

Error Installing DotNetNuke

Current Assembly Version: 05.00.00

ERROR: Could not connect to database specified in connectionString for SqlDataProvider

I don't have administrative rights on my machine, but VWD including SQL 2005 Express where setup with administrative rights. I don't have any other SQL server or ISS machine installed, only the server which came with VWD2008 Express.