The European Commission has imposed a 280.5 million (£193 million) fine on Microsoft after the software giant failed to comply with antitrust rules, saying that "no company is above the law".
The amount is at the upper range of expectations of the fine and follows a 2004 ruling which found Microsoft guilty of abusing its dominant market position within Europe.
EU officials then ordered the company to share information relating to its Windows operating system with its rivals, but today ruled that information so far supplied by the software firm has been inadequate.
"The commission is obliged to ensure compliance with EU law, and I have always underlined my determination to ensure that Microsoft fully implements the commissions March 2004 Decision," European competition commissioner Neelie Kroes explained.
"I have no alternative but to levy penalty payments for this continued non-compliance.
"Any businesses operating in the EU must obey EU law I sincerely hope that the latest technical documentation being delivered by Microsoft will finally bring them into compliance and that further penalty payments will not prove necessary."
The current penalty was calculated by backdating the daily fine that would have been payable by Microsoft to a warning issued by the commission in December, when officials told the company it would face fines of 2 million (£1.4 million) a day for non-compliance with their demands.
The European Commission said it would increase its fine to 3 million (£2.1 million) a day if Microsoft fails to comply with the commission's antitrust ruling by July 31st.
Microsoft, which maintains that it has complied with the demands of EU regulators, has said that it intends to deliver the last batch of documents relating to the requirements by July 18th.