C#

Bitmap bg;<br />
    bg=(Bitmap)Bitmap.FromFile(@"Your image.bmp");<br />
    bg.MakeTransparent(Color.White);

private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)<br />
   {<br />
	e.Graphics.DrawImage(bg,0,0,this.Width,this.Height);<br />
<br />
        //If you used an ImageList<br />
        //e.Graphics.DrawImage(imageList1.Images[backgroundIndex],0,0,this.Width,this.Height);<br />
   }

Bitmap bg;<br />
private void Form1_Load(object sender, System.EventArgs e)<br />
{<br />
bg=(Bitmap)Bitmap.FromFile(@"C:\Documents and Settings\sabry\Desktop\tt.bmp");<br />
bg.MakeTransparent(Color.White);<br />
}<br />
private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)<br />
{<br />
e.Graphics.DrawImage(bg,0,0,this.Width,this.Height);<br />
}

System.Drawing.Drawing2D.GraphicsPath gp=new System.Drawing.Drawing2D.GraphicsPath(new Point[]{new Point(0,0),new Point(200,0),new Point(100,200)},new byte[]{(byte)PathPointType.Start,(byte)PathPointType.Line,(byte)PathPointType.Line});<br />
  this.Region=new Region(gp);

public Form1()<br />
{<br />
InitializeComponent();<br />
Bitmap Img = new System.Drawing.Bitmap(@"C:\myPic.bmp");<br />
Img.MakeTransparent(Img.GetPixel(1,1));<br />
this.BackgroundImage = Img;   <br />
this.TransparencyKey = Img.GetPixel(1,1);<br />
}