A European Union court will decide on Monday whether Microsoft abused its near-monopoly position on the world's 1 billion computers and servers to push smaller competitors out of the marketplace.
The European Commission ruled in 2004 that Microsoft used its Windows operating system, running on 95 percent of the world's computers and servers, to choke off competition from rival makers of server software and streaming media software.
Microsoft challenged that decision, asking a special 13-judge Grand Chamber of the Court of First Instance to throw out the Commission's finding. It said the Commission was interfering with its right to design software as it saw fit.
The court will hand down its ruling on live television on Monday shortly after 9:30 am (0730 GMT), focusing on five aspects of the Commission's 2004 decision.
First, the court will rule whether to cut the 497 million euro ($689.9 million) fine the Commission imposed on Microsoft. Any change would have mostly symbolic value because the penalty makes no difference to Microsoft's bottom line.
Second, it will decide whether to overturn sanctions imposed on Microsoft for illegally bundling its Windows Media Player with the Windows operating system. Microsoft was ordered to sell a version of Windows without Windows Media Player. Few bought it.
Third, it will decide whether the underlying decision on bundling was incorrect, which would automatically cancel the sanctions. The Commission found Microsoft had bundled Windows Media Player to hurt such rivals as RealNetworks, which once dominated the field.
Today, media software is used to watch Google's YouTube, download Apple iTunes or listen to Webcasts. Fourth, the court will decide whether to throw out sanctions requiring Microsoft make its software run more smoothly with that of rival work group servers, the so-called "interoperability" issue.
The Commission says Microsoft has yet to comply with this sanction and has fined it 280.5 million euros so far for failure to do so, with more threatened. If the sanctions are invalidated, that would put an end to the continuing enforcement and likely require a return of the fine.
Finally, the court will decide whether to throw out the interoperability decision itself, which would automatically invalidate the sanction.
The Commission says Microsoft, by making its own servers interoperate with desktop PCs better than those of its rivals, drove others from the marketplace.
If the Commission's power is preserved, no matter whether the sanctions are thrown out, it will be able to press ahead against Microsoft on a series of other pending complaints. Otherwise, it may have to back off.
Companies around the world are waiting to see whether the court will cut into the Commission's power. In addition to Microsoft, the Commission has pending antitrust cases and complaints involving Intel, Qualcomm, Rambus and others.