procedure DrawTextOnDesktop(TextToDraw: string) ;
 var
    Handle: HWND;
    Dc: HDC;
    ACanvas: TCanvas;
 begin
    Handle := GetDesktopWindow;
    Dc := GetWindowDC(Handle) ;
    ACanvas := TCanvas.Create;
    try
      ACanvas.Handle := DC;
      BeginPath(ACanvas.Handle) ;
      ACanvas.Font.Color := clRed;
      ACanvas.Font.Name := 'Tahoma';
      ACanvas.Font.Size := 30;
      SetBkMode(ACanvas.Handle, TRANSPARENT) ;
      EndPath(ACanvas.Handle) ;
      ACanvas.TextOut(100, 500, TextToDraw) ;
    finally
      ReleaseDC(Handle, ACanvas.Handle) ;
      ACanvas.Free;
    end;
 end;