IN 2009 the European Commission carried out an investigation into Microsoft. The American software giant bundled Internet Explorer, its web browser, into Windows, the operating system in the great majority of personal computers. This, thought the commission, might be an abuse of its dominance in operating systems: buy a PC, and unless you took the trouble of choosing otherwise, you would browse the web through Explorer.

In December that year Microsoft promised the watchdog that until 2014 it would provide a "choice screen", asking European Windows users whether they wanted to install another browser. The screen first appeared in March 2010.

Jolly good—but Microsoft forgot to keep its word. On March 6th the competition commissioner, Joaquín Almunia, said he had fined it €561m ($732m) for not including the choice screen with 15m copies of Windows software between May 2011 and July 2012. Neither Microsoft nor the commission spotted the lapse. It seems that eventually other companies did.

The fine must sting all the more because Microsoft's transgression brought it little if any gain. Explorer has fallen behind Chrome, made by Google, and Firefox, made by Mozilla, a non-profit organisation (see chart). And people are doing more and more browsing on smartphones and tablets, the domain of Apple, Google and their browsers. Windows devices, which carry Explorer, have a minute share.

Microsoft's antitrust woes in Europe should have been over. In 2004 it was fined €497m for tying its media player and server operating systems with its PC system. In 2008 it copped another €899m penalty for failing to comply with the commission's ruling in that case. Lately it has been among the accusers—of Google, which Mr Almunia has been investigating since 2010.

He suspects Google of abusing a position in online search every bit as imposing as Microsoft's in PC operating systems. Bing, Microsoft's search engine, is a distant second (in Europe, very distant). The commissioner believes that Google may be favouring its own specialised services (eg, for flights or hotels) at rivals' expense; that its deals with publishers may unfairly exclude competitors; and that it prevents advertisers from taking their data elsewhere.

Mr Almunia asked Google to propose by the end of January ways of meeting his concerns. He has not yet said what it suggested or how he will respond. European antitrust cases have a habit of dragging on. Just ask Microsoft.