uses ShellApi;
begin
  ShellExecute(handle, nil, 'rundll32.exe', 
  'shell32.dll,SHHelpShortcuts_RunDLL AddPrinter', '',SW_SHOWNORMAL); 
end;

uses ShellApi, ShlObj;
procedure TForm1.Button5Click(Sender: TObject);
var
  PIDL:PItemIDList;
  Info:TShellExecuteInfo;
  pInfo:PShellExecuteInfo;
  WaitCode:DWord;
begin
  {Obtenemos PIDL de la carpeta virtual}
  {get PIDL of the virtual folder}
  SHGetSpecialFolderLocation(Handle,
                             CSIDL_PRINTERS,
                             PIDL);
  {Puntero a Info}
  {Pointer to Info}
  pInfo := @Info;
  {Rellenamos Info}
  {Fill info}
  With Info do begin
    cbSize := SizeOf(Info);
    fMask := SEE_MASK_NOCLOSEPROCESS 
             SEE_MASK_IDLIST;
    wnd := Handle;
    lpVerb := nil;
    lpFile := nil;
    {Parametros al ejecutable}
    {Executable parameters}
    lpParameters := nil;
    lpDirectory := nil;
    nShow := SW_ShowNormal;
    hInstApp := 0;
    lpIDList := PIDL;
  end;
  {Ejecutamos}
  {Execute}
  ShellExecuteEx(pInfo);
  {Esperamos que termine}
  {Wait to finish}
  repeat
    WaitCode := WaitForSingleObject(Info.hProcess, 500);
    Application.ProcessMessages;
  until (WaitCode <> WAIT_TIMEOUT);
end;