Microsoft failed Monday in its bid to overturn a European Commission antitrust ruling against it, when the European Union's second highest court dismissed the company's appeal and ordered it to pay the bulk of the Commission's legal expenses.

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The long-awaited decision by the Court of First Instance in Luxembourg supports the Commission, the E.U.'s top antitrust regulator, on the two essential aspects of the case.

The Commission was right to take action to prevent Microsoft from bundling in Windows Media Player into the Windows operating system, the court concluded. It was also right to force Microsoft to reveal interoperability information to makers of server operating systems.

An order for Microsoft to pay a fine of €497 million (then around $600 million) also still stands.

The only fault the court found in the Commission was the powers it granted to an independent monitoring trustee to oversee Microsoft's implementation of its 2004 antitrust ruling.

Brad Smith, Microsoft's top lawyer, said: "We'll study this decision carefully and if there are additional steps that we need to take to comply with it, we will take them."

European Commission President José Manuel Barroso welcomed the ruling. "This judgment confirms the objectivity and the credibility of the Commission's competition policy. This policy protects the European consumer interest and ensures fair competition between businesses," he said.

The Commission's allies also hailed the decision.

"This is a great day for European businesses and consumers," said Thomas Vinje, who heads the legal team for the European Committee for Interoperable Systems (ECIS). "This decision opens the prospect for dynamic competition in the software industry. No more user lock-in, no more monopoly pricing," he said.

Georg Greve, president of the Free Software Foundation Europe (FSFE), said: "Through tactics that successfully derailed antitrust processes in other parts of the world, including the United States, Microsoft has managed to postpone this day for almost a decade. But thanks to the perseverance and excellent work of the European Commission, these tactics have now failed in Europe."

Carlo Piana, FSFE's legal counsel, described the court ruling as "a milestone for competition. It puts an end to the notion that deliberate obfuscation of standards and designed lock-in is an acceptable business model, and forces Microsoft back into competing on the grounds of software technology."

Software developer Jeremy Allison, co-author of the open source print and file server Samba, also approved the ruling. "This is a very important day for the Samba team: we hope to finally compete on a level playing field, without being denied access to interoperability information. Samba would then be able to offer consumers real choice, with the benefits of software freedom," he said.

However, an industry group on Microsoft's side said the ruling was bad for small and medium-size enterprises (SMEs).

"The Commission just got a treat from the court, but SMEs and consumers will actually foot the bill. Microsoft did not win today, but it is European software developers and consumers that really lost," said Jonathan Zuck, president of the Association for Competitive Technology.

It will take several hours and days to get a true assessment of the implications, he said, suggesting that the detail of the ruling might yet contain a "silver lining" for SMEs.

"Following today's judgment, consumers and developers are unlikely to see the technologies they are demanding -- like voice recognition and multitouch interfaces -- integrated into Windows," he said.