How to create fully transprent windows in C# 2008??

using System;
using System.IO;
using System.Net;
using System.Windows;
using System.Runtime.InteropServices;
using System.Collections.Generic;

namespace WindowsFormsApplication1
{       public struct MARGINS
        {
            public MARGINS(int l, int r, int t, int b)
            {
                Left = l;
                Right = r;
                Top = t;
                Bottom = b;
        
            }
            public MARGINS(ref MARGINS m)
            {
                Left = m.Left;
                Right = m.Right;
                Top = m.Top;
                Bottom = m.Bottom;
            }
            public int Left;
            public int Right;
            public int Top;
            public int Bottom;
        }
    public class GlassHelper
    {
        [DllImport("dwmapi.dll", PreserveSig = false)]
        static extern void DwmExtendFrameIntoClientArea(IntPtr hwnd, ref MARGINS margins);

        [DllImport("dwmapi.dll", PreserveSig = false)]
        static extern bool DwmIsCompositionEnabled();


        public static bool ExtendGlassFrame(System.Windows.Forms.Form window, MARGINS margin)
        {
            if (!DwmIsCompositionEnabled())
                return false;

            IntPtr hwnd = window.Handle;
            if (hwnd == IntPtr.Zero)
                throw new InvalidOperationException("The Window must be shown before extending glass.");

            // Set the background to transparent from both the WPF and Win32 perspectives
            // SolidColorBrush background = new SolidColorBrush(Colors.Red);
            //background.Opacity = 0.5;
            window.BackColor = System.Drawing.Color.Black ;
              MARGINS margins = new MARGINS(ref margin);
            DwmExtendFrameIntoClientArea(hwnd, ref margins);
            return true;
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {

            GlassHelper.ExtendGlassFrame(this,new MARGINS(50,50,60,60));
            InitializeComponent();
            
        }

    }
}