EU antitrust regulators have told Microsoft not to repeat the mistake of denying consumers a choice of rival web browsers in its new Windows 8 operating system, in a dispute that has already cost the software giant more than a billion euros in fines.
EU competition commissioner Joaquin Almunia said he had spelt out his concerns to Microsoft about Windows 8, its new flagship software product which is set for release on Friday.
"I have precisely transmitted ... my concerns, what kind of presentation should be avoided if they don't want to take the risk of a new investigation," Almunia told a news briefing.
The company said it had taken heed of the warning, indicating its desire to draw a line under its decade-long battle with the European Commission.
"After discussions with the Commission, we are changing some aspects of the way the browser choice screen works on Windows 8 and will have those changes implemented when Windows 8 launches later this week," Microsoft spokesman Robin Koch said in a statement.
Almunia's warning came with charges that Microsoft had broken a promise to offer European consumers a choice of rival browsers in its previous version of Windows, which could result in a substantial fine.
Microsoft promised three years ago to offer browser choices, to settle an EU antitrust investigation and avoid a penalty that could have been as much as 10 percent of its global turnover.
But the European Commission said Microsoft had not fulfilled its pledge between February last year and July this year.
"If companies enter into commitments, they must do what they are committed to do or face the consequences. Companies should be deterred from any temptation to renege on promises or even to neglect their duty," Almunia told reporters.
Microsoft could face a significant fine as it is the second time it has failed to comply with an EU order.
A sanction could top $US7.4 billion ($A7.2bn) or 10 percent of its revenues for the fiscal year ending June 30, 2012 - but the final figure is expected to be lower, as the infringement covered a relatively short period of time.
Microsoft, which has already been penalised to the tune of €1.6 billion ($A2bn) in the last decade for infringing EU rules, apologised. It has four weeks to reply to the Commission's "statement of objections" or charge sheet.
"Although this was the result of a technical error, we take responsibility for what happened, and we are strengthening our internal procedures to help ensure something like this cannot happen again," the company said in a statement.