The European Commission has fined US computer giant Microsoft for defying sanctions imposed on it for anti-competitive behaviour.
Microsoft must now pay 899 million euros ($1.4bn; £680.9m) after it failed to comply with a 2004 ruling that it took part in monopolistic practices.
The ruling said that Microsoft was guilty of not providing vital information to rival software makers.
EU regulators said the firm was the first to break an EU antitrust ruling.
An investigation concluded in 2004 that Microsoft was guilty of freezing out rivals in server software and products such as media players.
The European Court of First Instance upheld this ruling last year, which ordered Microsoft to pay 497 million euros for abusing its dominant market position.
"Microsoft was the first company in 50 years of EU competition policy that the Commission has had to fine for failure to comply with an antitrust decision," Competition Commissioner Neelie Kroes said in a statement.
Last week, the firm announced that it would open up the technology of some of its leading software, including Windows, to make it easier to operate with rivals' products.
"As we demonstrated last week with our new interoperability principles and specific actions to increase the openness of our products, we are focusing on steps that will improve things for the future," Microsoft said.
Microsoft must now pay 899 million euros ($1.4bn; £680.9m) after it failed to comply with a 2004 ruling that it took part in monopolistic practices.
The ruling said that Microsoft was guilty of not providing vital information to rival software makers.
EU regulators said the firm was the first to break an EU antitrust ruling.
An investigation concluded in 2004 that Microsoft was guilty of freezing out rivals in server software and products such as media players.
The European Court of First Instance upheld this ruling last year, which ordered Microsoft to pay 497 million euros for abusing its dominant market position.
"Microsoft was the first company in 50 years of EU competition policy that the Commission has had to fine for failure to comply with an antitrust decision," Competition Commissioner Neelie Kroes said in a statement.
Last week, the firm announced that it would open up the technology of some of its leading software, including Windows, to make it easier to operate with rivals' products.
"As we demonstrated last week with our new interoperability principles and specific actions to increase the openness of our products, we are focusing on steps that will improve things for the future," Microsoft said.