procedure OpenURL(Url: string);
var
  ts: string;
begin
  with TRegistry.Create do
    try

      //Hier kommt die Fehlermeldung des Compilers
      rootkey := 'HKEY_CLASSES_ROOT';
      //Was muss ich anders definieren???

      OpenKey('\htmlfile\shell\open\command', False);
      try
        ts := ReadString('');
      except
        ts := '';
      end;
      CloseKey;
    finally
      Free;
    end;
  if ts = '' then Exit;
  // remove quotes and commandline parameters
  ts := Copy(ts, Pos('"', ts) + 1, Length(ts));
  ts := Copy(ts, 1, Pos('"', ts) - 1);
  ShellExecute(0, 'open', PChar(ts), PChar(url), nil, SW_SHOW);
end;