problem with local connection

I've just installed VS .NET 2005 and also installed sql Express that come along with it
when I tried to run a simple web page wih gridview that connect to the sql express with the table that I create and test it
status is "Tested connection suceeded" or test query is also successful but when I run I got the following message please help

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Cannot open database "customers" requested by the login. The login failed.
Login failed for user 'myServer\ASPNET'.

Description:An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details:System.Data.SqlClient.SqlException: Cannot open database "customers" requested by the login. The login failed.
Login failed for user 'USFER54-8B481CE\ASPNET'.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[SqlException (0x80131904): Cannot open database "customers" requested by the login. The login failed.Login failed for user 'USFER54-8B481CE\ASPNET'.] System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +739123 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +188 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +1956 System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) +33 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +170 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +349 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +181 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +170 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +359 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +28 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +424 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +66 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +496 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +82 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +105 System.Data.SqlClient.SqlConnection.Open() +111 System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +121 System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +137 System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable) +83 System.Web.UI.WebControls.SqlDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +1770 System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +17 System.Web.UI.WebControls.DataBoundControl.PerformSelect() +149 System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +70 System.Web.UI.WebControls.GridView.DataBind() +4 System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +82 System.Web.UI.WebControls.CompositeDataBoundControl.CreateChildControls() +69 System.Web.UI.Control.EnsureChildControls() +87 System.Web.UI.Control.PreRenderRecursiveInternal() +41 System.Web.UI.Control.PreRenderRecursiveInternal() +161 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1360

Thanks in advance for your help

ASPNet ('USFER54-8B481CE\ASPNET') user is not having access to the database. You can add ASPNet user to this database using management studio and then try accessing the site.

You can also try accessing the site using SQL Server User instead of Windows User.

sql