by Attila Kovacs - GExperts - https://plus.google.com/108426155215159556558/posts/5aerMRrx9ip

get-rid-of-orphan-Delphi-hint-windows.pas

  EnumWindows(@EnumWindowsProc, LPARAM(0));

function EnumWindowsProc(Wnd: HWND; Form: TForm): BOOL; stdcall;
var
  Buffer: array [0 .. 99] of Char;
  ClassName: string;
begin
  GetClassName(Wnd, Buffer, 100);
  ClassName := string(Buffer);
  if ClassName = 'TDesignerHintWindow' then
    SendMessage(Wnd, WM_CLOSE, 0, 0);
  Result := True;
end;