Transparent background on winforms?

I wanted to make my windows form transparent so removed the borders, controls and everything leaving only the forms box, then I tried to the BackColor and TransparencyKey to transparent but it didnt work out as BackColor would not accept transparent color. After searching around I found this at msdn:

SetStyle(ControlStyles.UserPaint, true);
SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
SetStyle(ControlStyles.SupportsTransparentBackColor, true);
this.BackColor = Color.Transparent;
this.TransparencyKey = BackColor;

Unhappyly it did not work either. I still get the grey or any other selected color background.

All I wanted to do is to have the windows form transparent so I could use a background image that would act as if it was my windows form.

I searched around here and saw many topics in regards opacity which is not what I am looking for and also saw some in regards this method I was trying but have not found an answer yet.

Hope anyone can light my path.

UPDATE:

image removed as problem is solved

The manner I have used before is to use a wild color (a color no one in their right mind would use) for the BackColor and then set the transparency key to that.

this.BackColor = Color.LimeGreen;
this.TransparencyKey = Color.LimeGreen;

A simple solution to get a transparent background in a windows form is to overwrite the OnPaintBackground method like this:

protected override void OnPaintBackground(PaintEventArgs e)
{
    //empty implementation
}

(Notice that the base.OnpaintBackground(e) is removed from the function)