The European Commission Wednesday levied a fine of €561 million ($733 million) on Microsoft for failing to keep its legally binding 2009 promise to offer European Windows users a choice of rival browsers.

Microsoft claimed an accidental technical glitch prevented the new Windows 7 Service Pack 1 from displaying the agreed browser screen of 12 alternative browsers between May 2011 and July 2012. The original deal was to show the browser screen until 2014.

The EC estimates that 15 million Europeans were never made aware that they could use a browser other than the default Internet Explorer. It also said that prior to May 2011 when the browser screen was available 84 million browsers were downloaded.

Europe's competition commission Joaquin Almunia said, "Legally binding commitments reached in antitrust decisions play a very important role in our enforcement policy. A failure to comply is a very serious infringement that must be sanctioned accordingly."

It is the first time the EC has fined a company for non-compliance with an agreement. It could have demanded 10% of Microsoft's annual revenues or roughly $7.9 billion but Microsoft cooperated with the agency shortening its investigation.

Microsoft's share of the European browser market has dropped to 24% since 2008, roughly half of what it was. Chrome now has an estimated 35% and Mozilla 29%.

Microsoft is doubtless the most fined company in the EC lists having now hit a total of €2.16 billion.

Intel holds the record for the single highest fine ever.

The EC is currently demanding concessions from Google to avoid antitrust action.