European regulators on Wednesday went dramatically further than their US counterparts by imposing a record fine of half a billion euros and product changes on US software giant Microsoft for stifling rivals.
The European Union's competition commissioner, Mario Monti, announced at the end of a five-year investigation that he was fining the world's biggest software company 497 million euros (611 million dollars) for abusing its dominant market position.
The Italian commissioner also ordered Bill Gates' titan to offer a European version of its all-conquering Windows operating system without the Media Player programme within 90 days.
And Microsoft was ordered to disclose "complete and accurate" data to enable rival companies to offer low-end servers that can work with Windows within 120 days.
The Seattle-based company, denying that it abuses its overwhelming dominance to crush competitors, has already vowed to appeal the verdict at the European Court of Justice, and to ask the court to suspend the sanctions.
Monti said the sanctions laid down a clear marker for the future conduct of Microsoft, which escaped fines in a US anti-trust investigation.
"Today's decision restores the conditions for fair competition in the markets concerned and establishes clear principles for the future conduct of a company with such a strong dominant position," he said.
And he told a news conference: "We are not expropriating Microsoft's intellectual property. We are also not breaking new legal ground neither in Europe nor in the US."
"I am confident that we have produced here a decision that will stand before any appeal," he added.
"I do not believe that Microsoft, with its resources and knowing of the allegations outlined during the course of the investigation over the past five years, was not aware that it could be breaking EU competition law."
The unprecedented size of the financial penalty might not hurt Microsoft, which has cash reserves of some 53 billion dollars.
But enforced changes in Europe to its Windows operating system, which powers nine out of 10 of all personal computers, will.
After largely settling its anti-trust problems at home through a hotly disputed deal with the US Justice Department, Microsoft sees no reason why it should undergo a drastic product overhaul in Europe.
Being forced to unbundle Media Player would be the thin end of the wedge for a company that has placed an all-in-one suite of applications at the heart of its hugely successful business strategy.
To date, the biggest fine levied by the commission on a company for breaking EU competition rules was a 462-million-euro penalty against the Swiss chemical firm Hoffman-Laroche in 2001, for orchestrating a vitamins cartel.
And the Microsoft penalty will dwarf the previous biggest fine for abuse of dominant market position - 75 million euros - levied in 1991 against Swedish packaging firm Tetra Pak.
In the United States, Microsoft was accused of similarly unfair practices notably in bundling its Internet browser program with Windows.
But after a four-year anti-trust probe, the US Justice Department reached a hotly contested deal with Microsoft in 2001 that forced the firm to share some technical data with rivals but stopped short of fines.
The agreement was upheld by a US judge a year later, leaving competitors to transfer their hopes for redress to the European Commission's own investigation.