Hint Window - How to recognize ?

I want to hide all visible windows, so I enumerate all windows into a list
then hide them all and show them when my application closes.  Occasionally I
capture a hint window which when shown later ends up as an orphaned empty
window on the desktop ... so how do I identify a hint window so that I can
exclude them ?

    fWndList  := TList.Create;
    Wnd       := GetWindow(GetDesktopWindow, GW_CHILD);
    while (Wnd <> 0) do begin
      if IsWindow(Wnd) and
           IsWindowVisible(Wnd) and
             IsWindowEnabled(Wnd) and
               (Handle <> Wnd) then begin
        fWndList.Add(Pointer(Wnd));
      end; {if}
      Wnd := GetWindow(Wnd, GW_HWNDNEXT);
    end; {while}

Andrew