SQL server name not found:Admin-PC\MSSQLSERVER,1433

Hi guys,
I develop a csharp smart device project.My code is:
using System;
using System.Linq;
using System.Data.SqlServerCe;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace ModeDifféré
{
public partial class Form6 : Form
{
public Form6()
{
InitializeComponent();
}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{

}

private void Form6_Load(object sender, EventArgs e)
{

string sConnection = @"Data Source=Admin-PC\MSSQLSERVER,1433;Initial Catalog=GMAO;User ID=sa;Password=sa;";
string sSQL = "SELECT Nbt FROM 4BT; ";
SqlConnection conn = new SqlConnection(sConnection);
SqlCommand comm = new SqlCommand(sSQL, conn);
SqlDataReader dr = null;
try {
comm.Connection.Open();
dr = comm.ExecuteReader();
while (dr.Read())
comboBox1.Items.Add(dr[0]);
}
catch (SqlException ex)
{
MessageBox.Show(ex.Message);
return;
}

dr.Close();
comm.Connection.Close();
}
}
}

When running this program and after turning off my Firewall(to enable all connections including TCP connections to SQL SERVER),This error appears
Specifid SQL server name not found:Admin-PC\MSSQLSERVER,1433 Thanks
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Notes!!!
I work with:
- SQL SERVER 2005 standart edition
-Visual Studio 2008 entreprise edition
-windows Se7en