A European court confirmed yesterday that it will rule on September 17th on whether software giant Microsoft broke European Union anti-trust regulations.

Microsoft is appealing to the Court of First Instance against a landmark 2004 decision by the European Commission, which ordered the company to change its business practices and which fined it €497 million.

The software giant was subsequently hit with an additional €280.5 million last July because the commission said that it had continued its anti-competitive practices.

The Luxembourg-based court, the second-highest in the EU, confirmed that the ruling will come on September 17th, the final working day before the retirement of court president Bo Vesterdorf, who is presiding over the case.

The EU's executive commission found in 2004 that Microsoft had broken competition rules by abusing the dominance of its Windows product, muscling out competitors unable to make software that would work smoothly on the operating system.

Despite Microsoft's appeal, it was still liable to implement the commission's decision, which involved giving rivals information needed to make their software work with Windows.

Three years on, the commission has repeatedly warned Microsoft that it has failed to comply with the 2004 decision because it supplied insufficient information.

Commission spokesman Jonathan Todd said the EU executive was still looking into those charges, after Microsoft prepared a set of technical documents for rivals and set fees for their use.

"We haven't yet reached a view as to whether or not the technical documentation made available is enough, or indeed as to whether we're happy with the fees charged for licensing. We're still investigating that," said Mr Todd.