The Windows 7 service pack 1, rolled out between mid-2011 and mid-2012, failed to offer consumers a choice of browser, leading to the EU investigation that resulted in today's fine.
Microsoft said the failure was the result of a technical error and that procedures have since been tightened.
In what was seen as an acknowledgement of the severity of the mistake, the board cut the bonus of chief executive Steve Ballmer last year, according to company's annual reports.
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The 'Let Our Kids Be Kids' campaign wants parents to keep their children off school saying they are "over-tested and over-worked".
Nicky Morgan is expected to defend the proposal when she faces questions at the National Association of Head Teachers' annual conference.
Phone charges in the European Union will drop by about 75 per cent from today as part of an interim cap ahead of a full ban next year.