In 2009, the European Commission's competition directorate agreed to close an investigation into allegations that Microsoft abused its dominant position in desktop software by tying Internet Explorer to Windows.
Microsoft agreed to include a browser choice screen in Windows. But the commission said Wednesday that Microsoft failed to offer that screen in a Windows 7 service pack software update from May 2011 to July 2012, in violation of the agreement.
"If companies agree to offer commitments which then become legally binding, they must do what they have committed to do or face the consequences -- namely, the imposition of sanctions," Joaquin Almunia, the European Commission's vice president in charge of competition policy, said in announcing the fine of 561 million euros.
It was the first time European regulators fined a company for failing to comply with an agreement, he said.
The fine comes on top of approximately $2.5 billion in levies from European officials on the software giant for antitrust violations in a series of high-profile cases dating to the early 2000s.
Microsoft said it took full responsibility for what it called a "technical error" and apologized for the problem.
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