List available Screen Resolutions

procedure TForm1.Button1Click(Sender: TObject);
var
  DC: THandle;    // display context
  Bits: Integer;    // bits per pixel
  HRes: Integer;    // horizontal resolution
  VRes: Integer;    // vertical resolution
  DM: TDevMode;   // to Save EnumDisplaySettings
  ModeNum: Longint;    // video mode number
  Ok: Bool;
  fre: Integer;    // refresh rate
begin
  DC := GetDC(Handle);

  Bits := GetDeviceCaps(DC, BITSPIXEL);
  HRes := GetDeviceCaps(DC, HORZRES);
  VRes := GetDeviceCaps(DC, VERTRES);
  fre := GetDeviceCaps(DC, VREFRESH);

  // Show Current Resolution
  Edit1.Text := Format('%d bit, %d x %d', [Bits, HRes, VRes]);

  ReleaseDC(Handle, DC); // Show all modes available ModeNum := 0;  // The 1st one
  ModeNum := 0;
  EnumDisplaySettings(nil, ModeNum, DM);
  ListBox1.Items.Add(Format('%d bit, %d x %d bei %d Hz',
                           [DM.dmBitsPerPel,
                            DM.dmPelsWidth,
                            DM.dmPelsHeight,
                            Dm.dmDisplayFrequency]));

  Ok := True;

  while Ok do
  begin
    Inc(ModeNum); // Get next one
    Ok := EnumDisplaySettings(nil, ModeNum, DM);

    ListBox1.Items.Add(Format('%d bit, %d x %d bei %d Hz',
                              [DM.dmBitsPerPel,
                               DM.dmPelsWidth,
                               DM.dmPelsHeight,
                               Dm.dmDisplayFrequency]));
  end;
end;