Microsoft on Friday said it has appealed a $1.39 billion fine imposed in February by the European Commission for the company's failure to comply with a 2004 antitrust order.
Microsoft filed an application with the Court of First Instance in Luxembourg to annul the Commission's decision.
The fine had marked the tentative end to a long-running fight between the European Union and Microsoft, triggered by a 1998 complaint by Sun Microsystems. Sun alleged Microsoft was refusing to supply all the information servers need to work with its market-dominating Windows operating system.
Microsoft later made the information available to rivals, but the EU said it charged "unreasonable prices" until last October. European antitrust regulators have also required the Redmond-based company to sell a version of Windows without media player software.
In all, the company has been fined just under $2.63 billion by European regulators over the years.
Microsoft's tussles with the EU were renewed when regulators launched new probes in January. The European Commission is examining whether Microsoft illegally gives away its Internet Explorer browser for free with Windows, and whether the software maker withheld information from companies that wanted to make products compatible with its software, including Office word processing and spreadsheet tools and some server products.
Since then, Microsoft has pledged to make those protocols freely available for noncommercial uses and available at low royalty rates for commercial software developers.