When Microsoft conceded defeat in its nine-year antitrust battle with Europe’s competition authorities, another legal challenge became inevitable. Indeed, emboldened by the software giant’s submission, its rivals have persuaded Brussels to launch a second investigation with potentially bigger consequences for markets in desktop and internet applications. There may be a case for Microsoft to answer. But the European Commission should try to avoid another protracted legal fight.

Neelie Kroes, competition commissioner, should give complaints by IBM, Oracle and Sun Microsystems a fair hearing. Their allegation that Microsoft has abused the dominance of its Office product by unfairly keeping secret information to hinder the interoperability of rival software is a serious charge. So is the separate claim by Opera, the Norwegian browser company, that Microsoft illegally linked Internet Explorer to its Windows system.