The European Union is laying the smackdown all over Microsoft in the form of a hefty $732 million fine from its competition watchdog arm. The European Commission says the company failed to keep its promise to offer its 15 million Windows users a choice of Web browser other than Internet Explorer. That’s how a watchdog says “woof!”

To rub salt in that costly wound, the commission said Microsoft is the first company to go break a voluntary agreement with regulators. But Microsoft is no stranger to the EU’s ire — a previous fine for  €1.64 billion was issued when it didn’t provide rivals with information at fair prices and for tying its media player to Windows, reports the Wall Street Journal.

The EU’s competition chief is being clear that the Microsoft fine is serving as a warning shot to other companies who might be tempted into noncompliance.

“Such a breach is, of course, very serious, irrespective of whether it was intentional or not, and it calls for a sanction,” he said in a statement. “I hope this decision will make companies think twice before they even think of intentionally breaching their obligations or even of neglecting their duty to ensure strict compliance.”

Microsoft was supposed to offer a “choice screen” for consumers using Windows until 2014 that would let them choose another browser. At first, that seemed to be happening as planned. But then regulators got a complaint about it and found that the choice was gone, poof, not there since some point between February 2011 and July 2012.

Microsoft is calling the removal a “technical error” and says it’s accepting responsibility for that. While the commission says it can see how maybe Microsoft didn’t do anything bad on purpose, it’s going to start overhauling its own monitoring procedure instead of relying on companies to provide their own compliance reports.

Although some computer savvy users could no doubt go find their own choice of browser without a prompt telling them to do so, not everyone has that kind of technological know-how. It’s on the behalf of those consumers that the EU is acting. Because no one should be stuck with Internet Explorer, or any Web browser, against their will.

EU Fines Microsoft $732 Million [Wall Street Journal]

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