Microsoft must now pay a record 899m euros ($1.4bn; £680.9m) after it failed to comply with a 2004 ruling that it abused its dominant market position.

The ruling said that Microsoft was guilty of not providing key code to rival software makers.

EU regulators said the firm was the first to break an EU anti-trust ruling.

The fines come on top of earlier fines of 280m euros imposed in July 2006, and of 497m euros in March 2004.

"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.

Future improvements?

An investigation concluded in 2004 that Microsoft was guilty of freezing out rivals in products such as media players, while unfairly linking its Explorer internet browser to its Windows operating system at the expense of rival servers.

The European Court of First Instance upheld this ruling last year, which ordered Microsoft to pay 497m euros for abusing its dominant market position.

DISPUTE TIMELINE March 2004: EU fines Microsoft 497m euros and orders it to release key Windows code to rival software developers September 2004: Microsoft tries to have the ruling temporarily suspended April 2006: Microsoft appeals the ruling in the European Court of First Instance September 2007: Microsoft loses its appeal

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.

Further cases

But the firm is still being pursued by Brussels.

Last month, the European Commission launched two new anti-competition investigations against Microsoft into similar issues.

The first will look at whether there are still problems regarding Microsoft abusing its dominance of the PC market to grab market share of the internet.

The Commission will also investigate the continued interoperability of Microsoft software with rival products.

Below is a selection of your comments:

Why should Microsoft have to pay fines for something like this? All manufacture and trade is competition whether you want to accept it or not. If you fine Microsoft for competition then you have to fine every company and firm in Europe for competing with other companies and trying to be better than them. Some are always going to be better and you can't stop it from happening.

Elias Lammi, Vammala, Finland

Last time I checked Microsoft was worth somewhere in the region of $350bn, so a fine of $1.3bn is nothing; it's less than 0.3% of their overall wealth and hardly a deterrent. Should the EU feel the need to do this again, they should strive to impose a fine that has a more noticeable effect on the company's turnover. Something that would make the board members and share holders sit up and take notice.

Stephen Sweeney, London

Microsoft have every right to compete the way they want. If they reveal the key window code, how can they sustain competitiveness. Did any other company teach them the code? No, it is one of the rare resource, where others failed in acquiring such ideas and intellectual capital. I hope EU is not going to fine Microsoft for not helping its competitors to acquire working culture which embedded down the company.

zubair, Melbourn/Australia

Not enough. Microsoft has been getting away with uncompetitive behaviour for far too long. They should no longer be allowed to sell any product without publishing every line of source code.

Brian Beesley, UK

I think it is a bad ruling because Microsoft is being charged for not sharing their OWN code they wrote. Microsoft has every right not to share what they wrote. There's many other platforms out there for companies to write code for. There are many alternatives to web browsers and media players to download off the internet to begin with, so I don't see how this is a problem.

Nathan Vorgang, West Lafayette, IN, USA

I believe that the fine is too small for Microsoft.

Mohammad Bashir, Philadelphia, PA USA

I find it amazing that we have such ridiculous laws!! Why are we punishing a company for being good?? It's not Microsoft's fault that no-one else has come up with products that can compete...

Andy, Bracknell

Microsoft MUST be brought to account for its' practice of dominating by exclusion. If the company, Microsoft, continues to practice in a manner which refuses to be competitive, then it should be excluded from the EU. Nicholas Carton, USA

Nicholas Carton, Saint Louis, Missouri USA

I find it amazing that the EU can put sanctions on a company, who are to them ''anti-competition'' Yet have a complete monopoly on money in the form of the Euro. If it didn't make me laugh, it'd make me cry!

Richard Wilkins, Westbury, Wiltshire, Uk.

Definitely agree with the European Commission, even though I am employed as a microsoft .net developer.

Iain, Truro/UK

I very much agree with the decision of the European Commission. Microsoft, throughout its history, has been guilty of abusing its de facto dominance of pc operating systems. The US Federal Government has always favoured the company's interests over the customers and so the market abuse has continued. Microsoft must learn to compete rather than try to snuff out or take over competitors and companies with technology that they want.

R W Bater, Sutton Coldfield, West Midlands

I do not agree with the EU. Whom is the judgement awarded too? The EU or does it go to the Microsoft competitors? What happened to innovations and property protection? Like a number of things coming out of Brussels it does not make sense.

Hans K Vieregge, Aviemore , Great Britain

I am glad that Microsoft have been fined, if they had made the code open suorce, then they would not have been the main target for hackers,and may have ended up with a better product. How many times have you heard of Linux software being hacked? its not!! as all the lines of code are open source. If you have a problem with Linux you can actually converse with the person who wrote the code. This is not possible with Windows. If you use Linux or a Unix based operating system, you will be less likely to be hacked.

Ian, London

I think the fines are ridiculously high and that the EU is going after Microsoft because its a good American business. Sure Microsoft was a little arrogant but the fines are way to high.

Charles Parker, Des Moines Ia. USA