Microsoft's Windows 7 (download) is stirring fresh complaints of anticompetitive behavior from rivals who say the new version of the operating system gives unfair advantage to Internet Explorer browser. "Our initial review suggests this is a blatant use of the Windows operating system to change the market dynamics of browser usage," Mitchell Baker of Mozilla. No-one at Microsoft could immediately be reached for comment. Opera, echoed Mozilla's complaints about Windows 7, the paper said, reports eWeek.