Microsoft is facing a new investigation by the European Commission, this time into whether the software giant has abided by anti-trust commitments it made in a 2009 settlement.
The investigation follows claims that Microsoft failed to provide Windows users with a choice of default browser choice, as it had promised to do, when it updated Windows 7 with Service Pack 1.
The company has been warned that the penalties for non-compliance will be "severe".
In a statement, Microsoft blamed a "technical error" for the breach. "Due to a technical error, we missed delivering the BCS [browser choice screen] software to PCs that came with the Service Pack 1 update to Windows 7," admitted Microsoft in a statement.
However, Microsoft had claimed in a report to the commission in December that it was still providing users with the choice screen. In its statement, the company said that it still believed that was the case when that submission to the commission was made.
The initial anti-trust investigation has been sparked by a 2007 complaint from browser software maker Opera Software about browser access in Microsoft's operating systems. In Windows XP and earlier operating systems, Microsoft had integrated its own browser, Internet Explorer, so tightly into the operating system that it was judged to give Microsoft an unfair advantage in browser software.
EU competition commissioner, Joaquin Almunia, warned that the sanctions against Microsoft could be tough if the new investigation confirms a breach of compliance.
According to web browser maker Opera Software, the initial implementation of the browser choice screen in 2010 resulted in a surge in downloads, boosting usage of the company's browser by about 50 per cent.
However, it also complained that browser choice was buried amid a number of configuration screens.
Since the settlement, though, Internet Explorer has continued to be pegged back in terms of market share, with Google's Chrome now running a close second globally. The open source browser Firefox is estimated to have a 20 per cent global market share, while Opera typically weighs in at just two per cent – although it is popular in some eastern European and central Asian countries such as Ukraine, Belarus and Uzbekistan.