Try this:
System.Windows.Forms.Cursor.Position = new Point { X = xxx, Y = yyy };
Or try to use the native WinAPI for XP (or earlier):
[DllImport("user32.dll")]
public static extern long SetCursorPos(int x, int y);
public void SetCursorPosition(Point p)
{
SetCursorPos(p.X, p.Y);
}