US software giant Microsoft faces yet more heavy fines after it promised to offer clients a choice of web browser but has failed to do so, the EU\'s competition commissioner said Monday. Microsoft apologised in July for a \"technical error\" as the EU launched a probe into why 28 million users of the Windows 7 operating system were unable to choose between the company\'s default Internet Explorer and other browsers. It has not made the change so far and inevitably faces more fines -- to follow some of the heaviest EU penalties ever -- if it does not act soon, Commissioner Joaquin Almunia told AFP in an interview. Microsoft committed in 2009 to provide Windows users in Europe a \"choice screen\" enabling them to pick an alternative web browser until 2014. The screen, however, has been missing from an update to Windows 7 since February 2011 and the Commission has run out of patience after launching a formal probe in July. \"It is easier to make progress in our investigation if a company which has broken competition rules recognises the fact,\" Almunia said. \"The fault is there, it has been there for more than a year and it is clear that we need to react. \"It is not only the distortion of competition during this period which concerns us; it is very serious, from my point of view, that the remedies imposed on Microsoft have not been applied,\" he said. The Commission planned \"to act very firmly,\" he added. The EU fined Microsoft 899 million euros ($1.2 billion) in 2008 for failing to comply with an order to share product information with rivals so that their software can work with Windows.