The promise from Microsoft was to include a choice of browser in their Windows operating system for European customers, and the European Commission believes that hasn't come to pass in the operating systems released during May 2011 and April 2012. 

This means that 15 million users were not presented with an option to use another browser than the Internet Explorer included in the operating system.

The competition commissioner Joaquin Almunia highlights that the promises made during reconciliation are not taken lightly.

"Breaking a promise made is a serious offense, and the sanctions have to be in scale according to that." Almunia said in his statement.

As such Microsoft's sanctions were relatively reasonable, because the commission could've given Microsoft a fine as big as 10% of their international sales, which would be around 6 billion euros. The commission isn't done with this, because they're wrestling with Google for ranking certain search results.