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The European Commission suspects Microsoft is breaching the antitrust agreement to give customers a choice of internet browser on its Windows 7 operation system.

Microsoft was sent an official complaint a few days before it starts selling its new Windows 8 system. The world’s leading software producer may be fined for breaking the terms of the 2009 agreement, requiring it to display a choice of browsers, the regulators said in an e-mailed statement today.

Under the terms of the 2009 agreement, Microsoft must display a choice of the 12 most widely used browsers for users to install in addition to, or instead of, Microsoft’s Internet Explorer.

Earlier this year EU Competition Commissioner Joaquin Almunia accused Microsoft of misleading regulators by failing to display a browser choice screen since February 2011. The company denied any wrongdoing and blamed a technical error for not showing the choice screen to some 28 million computers running Windows 7.

"We take this matter very seriously and moved quickly to address this problem as soon as we became aware of it," the company said in a statement.

Meanwhile Microsoft has already been fined 1.68 billion euros in EU antitrust probes. Microsoft paid an 899 million-euro fine in 2009 and agreed to offer access to rival browsers on its operation systems.