In all, Microsoft has now paid €2.2 billion in fines to the Commission since 1998, when regulators opened their first investigations into the company after Sun Microsystems complained it had been denied access to technical documents. Over the years, the EU has broadened its investigation to include whether Microsoft had abused Window's near-monopoly over the market for computer operating systems to corner other markets, including server software, streaming media software, and Internet browsers.
Anthony Sabino, an antitrust lawyer and professor at St. John's University, said the Commission was right to fine Microsoft for the latest lapse, but the size of the penalty seemed "disproportionate...perhaps even petty, given that Microsoft has paid its fines and yielded to all the demands of the EU."
"They have been slow to acknowledge that, while powerful, Microsoft is not invincible," he said.
Sabino added that Microsoft may be paying the price in part for its aggressiveness in the past in testing the limits of what regulators will tolerate.
Given the length of time the latest violation went on, and the number of users affected, "it does strain credibility" that Microsoft wouldn't have known it had failed to keep its part of the agreement, Sabino added.
For its part, Microsoft was apologetic.
"We take full responsibility for the technical error that caused this problem and have apologized for it," the company said in a statement. "We provided the Commission with a complete and candid assessment of the situation, and we have taken steps ... to help avoid this mistake — or anything similar — in the future."
Microsoft's Internet Explorer still has a 56 percent market share for Internet browsers on personal computers, according to statistics by Net Applications. Mozilla's Firefox has 20 percent while Google's Chrome has a 17 percent share. Microsoft is required to continue to offer consumers a choice of browsers through 2014.