SQL SERVER 2005 + ASP.NET 2.0: Problems With Data.SqlClient.SqlConnection --&> Login Failed For User 'username'

I have lots of problems with the connection. I've connected many dropdownlists to the database and i didn't have problems at all. I also try an example of an ASP.NET book:

<asp:SqlDataSource ID="SqlDataSource1" runat="server"

ConnectionString= "<%$ ConnectionStrings:CIPPEC%>"

InsertCommand=

"INSERT INTO

[member] ([first_name], [last_name], [malefemale], [yearborn])

VALUES

(@first_name, @last_name, @malefemale, @yearborn)">

<InsertParameters>

<asp:FormParameter Name="first_name" Type="String"

FormField="FirstTextBox" />

<asp:FormParameter Name="last_name" Type="String"

FormField="LastTextbox"/>

<asp:FormParameter Name="malefemale" Type="Int32"

FormField="MFRadioButton" />

<asp:FormParameter Name="yearborn" Type="Int32"

FormField="YearDropDown" />

</InsertParameters>

</asp:SqlDataSource>

And it worked well.  But when i try to connect my page with:

Dim connect As New Data.SqlClient.SqlConnection( _

"Server=glgrand-arSQLEXPRESS;UID="WindowsStartupUser";password="WindowsStartupPass"; database=CIPPEC")

connect.Open()

Dim cmd As New Data.SqlClient.SqlCommand( _

"INSERT PRUEBA (PersonaJuridica, NombreRazonSocial, Nombre, Segundo_nombre, Apellido) " & _

"VALUES (txtPerJur, txtRazSoc, txtName, txtSecondName, txtApellido)", _

connect)

cmd.ExecuteNonQuery()

connect.Close()

The error message says: Login failed for user 'username'.

I tried lots of things but it didn't work:

In SQL Configuration Manager:

Client Protocols: TCP/IP and Named Pipes are enabled.

In SQL 2005 Services: Server Properties: Built-in Account: Local System

SQL Server Surface Area Configuration: Remote connections: Using both TCP/IP and Name Pipes connection is selected.

In SQL Management Studio i created a new login glgrand-ar/UserStartupName , with sysadmin server role and user mapping my CIPPEC database.

I don't know what else i could try, i tried it at home and at work and i couldn't connect to my database and make an INSERT. It stops at Connect.Open() with the error that i wrote in this subject message.

It's evident that i'm doing something wrong (because i'm new): Could you please help me with a solution and explain me what are the data that i have to put on the Data.SqlClient.SqlConnection ?? I'm using the Windows authentication: i'm putting my username and password and it doesn't worked.

Thank you!!