Are you sure?
Here's a tutorial, which might help:
http://www.switchonthecode.com/tutorials/csharp-snippet-tutorial-how-to-draw-text-on-an-image
(edit)
Try starting from basics: I just created a new forms application and changed the code in Form1 to this:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
this.Paint += new PaintEventHandler(Form1_Paint);
}
void Form1_Paint(object sender, PaintEventArgs e)
{
e.Graphics.DrawString("hello", new Font("Arial", 36), new SolidBrush(Color.FromArgb(255,0,0)), new Point(20,20));
e.Graphics.DrawString("world", new Font("Arial", 36), new SolidBrush(Color.FromArgb(0,0,255)), new Point(30,30));
}
}
It works as expected, with a transparent background for the text.