What was the court ruling about?

The European Court of First Instance dismissed an appeal by Microsoft against the landmark antitrust ruling handed down by the European Commission in March 2004. Brussels found Microsoft guilty of abusing its dominant position by clamping down on competition in the media player and server software markets. The Commission said the group had illegally bundled its own Media Player program into Windows; it also found Microsoft had refused to supply crucial interoperability information about Windows to rival companies.

A complete victory for the Commission then?

Not quite. The court annulled a minor part of the Commission ruling relating to the powers of the monitoring trustee, the independent expert responsible for checking that Microsoft is in compliance with the 2004 ruling. However, on all the main points - those that matter in future cases - the regulator scored a resounding win.

Is this the end of the road for Microsoft?

No. The group can still appeal to the European Court of Justice, the Union's highest court. But it can only attack points of law, not factual errors, which means success is pretty remote. Moreover, Monday's ruling is very tightly and comprehensively argued - as one would expect after more than a year of deliberations by 13 of the continent's most respected judges.

So what is the Commission going to do next?

The Brussels watchdog has been hugely strengthened by yesterday's ruling. Its first priority will be to ensure that Microsoft finally complies with the 2004 ruling, which means that a further big fine is likely before the end of the year. Secondly, it now has all the legal backing it needs to pursue fresh cases against Microsoft, in particular relating to the new Vista operating system. Competitors have already complained about Vista to the Commission, and their complaints will now almost certainly be turned into formal investigations. If Microsoft wishes to escape further fines, it will have to address whatever demands the Commission throws at it next.

Microsoft claims other groups such as Apple, IBM and Google will be next in line. Is that true?

Neelie Kroes, the EU competition commissioner, was at pains to stress that the Microsoft case was "exceptional" - and indeed none of the above companies has a similarly imposing and stable monopoly. In the long run, however, one of the central arguments of the Commission's ruling - namely that dominant companies have a duty to ensure that rival products can function properly with their offering - could be turned against Apple's iPod and iTunes platform as well. Google's ever-growing market power too could eventually lead to closer scrutiny by Brussels. But such investigations would be at least some years away, and depend on the companies' continuing dominance in their field. Microsoft's problems, meanwhile, are very immediate.

And what about all that money that the Commission has bagged?

In the initial ruling, Microsoft was ordered to pay a record €497m antitrust fine. Last year, the group was fined an additional €280.5m for failing to respect the 2004 ruling. All that money has until now been parked on a blocked, interest-bearing account and would have been paid back to the group if the appeal had been successful. The funds will now be transferred into the EU budget, in turn reducing the bills of European taxpayers.