Firms will soon be able to buy Microsoft's Windows software without its own multimedia player pre-installed, following a crucial court EU decision yesterday.

The ruling will also force Microsoft to share the data protocols - software that enables programmes to run on the Windows operating system - with its rivals.

The decision by the European Court of First Instance marks the latest step in a battle between Microsoft and the European Commission.

The EC has found it guilty of abusing its dominant position in the operating system market.

The court upheld the penalties that were imposed by the European Commission's executive on Microsoft in March.

Its ruling, which is a blow to Microsoft, will force it to immediately change some of its business practices.

Microsoft Ireland's chief executive, Mr Joe Macri, described the ruling as "very disappointing" but said the company would comply with it.

"We are clearly going to make an alternative version of Windows available in the EU without Media Player installed," said Mr Macri.

The European Commission found Microsoft bundled its own audio-visual software, Media Player, to cripple rivals such as RealNetworks's RealPlayer, which it has overtaken as the dominant player in the software industry.

Now some versions of Windows will be shipped to computer makers without audiovisual software.

This is a decision the Commission designed to prompt manufacturers to choose among audiovisual offerings instead of accepting the Windows bundle.

The Commission also ordered Microsoft to share data protocols with makers of servers that are used in offices to access files and run printers.

This action is intended to enable firms to develop products to interact better with Microsoft products.

It is estimated that more than 90 per cent of the world's desktop computers use Microsoft Windows, which provides a platform for computer users to access other programmes.

The court's decision yesterday centred on whether Microsoft should be forced to comply with the remedies proposed by the Commission before a full appeal is heard.

Microsoft had argued that forcing it to unbundle Media Player from Windows would cause it "irreparable harm".

But Court of First Instance president Bo Vesterdorf ruled that: "Microsoft has not demonstrated specifically that it might suffer serious and irreparable damage... The application must therefore be dismissed in its entirety."Microsoft's general counsel, Mr Brad Smith, nevertheless, urged the Commission to consider fresh settlement talks, arguing the judge had found some merit in Microsoft's arguments on the substance of the case.

"Is there enough here for the Commission to restart settlement negotiations?" he asked.

"There's nothing here to guarantee that either side is going to win at the end of the day."

But European Commission competition spokesman Mr Jonathan Todd said the court decision upheld the effectiveness of antitrust action and the EU executive was "not in a process of renegotiation".