The main topics of interest are expected to be decisions relating to two issues raised by the Commission's March 2004 order against Microsoft, which included a $613 million fine and determinations that the company engaged in a number of anticompetitive practices.

One issue to be addressed by the court deals with whether Microsoft stifled competition by bundling its Media Player with Windows, the market's dominant operating system. The other issue focuses on whether Microsoft provided adequate interoperability protocol information to competitors.

If the court hands the Commission an overwhelming defeat on both the interoperability and Media Player issues, the Commission could find itself neutered, say legal experts.

In recent years, the Commission has aggressively pursued or investigated other technology industry titans, including chipmaker Intel, which faced allegations the company wooed customers with marketing dollars in exchange for their exclusive use of Intel chips. The Commission also took on mobile-phone chipmaker Qualcomm over antitrust issues surrounding its patents for its 3G chipsets, and recently began an antitrust review of Google's proposed $3.1 billion acquisition of online ad company DoubleClick.

Given the Commission's fearlessness in taking on major technology companies over competitive issues, a major defeat in court may leave it with the "wind taken out of its sails," noted Thomas Vinje, an antitrust attorney with Clifford Chance in Europe. The Commission, as a result, may temper the pace and energy with which it pursues cases, he noted.

But should the Commission soundly defeat Microsoft, legal observers say, it's doubtful European regulators will suddenly go on a rampage and pursue marginal antitrust cases.

"The effect of a really big loss would be greater than the effect of a really big win for the Commission," Vinje said.

The $613 million fine called for in the March 2004 order was increased by $357 million last year, after the Commission alleged the software giant had not complied with its original ruling. The Court of First Instance will also issue a decision on the multimillion-dollar fines.

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The court's decision is also expected to have some affect on the Commission's view toward other Microsoft products it is currently investigating, such as the Vista operating system, said Michael Reynolds, an antitrust attorney with Allan & Overy in Europe. The software giant announced in October that it made changes to Vista to accommodate concerns raised by antitrust regulators in Europe and South Korea.

"There already has been some intervention by the Commission," Reynolds said. "But everyone wants to see what the court says, before (finalizing) negotiations with the Commission."

While the court's ruling may have an affect on how antitrust cases are addressed by the EC, one legal expert said it is unlikely Google, Intel, Rambus or Qualcomm will be affected by the Microsoft decision next week.

Google's market share is far lower than that of Microsoft and no barriers exist to prevent users from migrating to another search engine, said Maurits Dolmans, an antitrust attorney with Cleary Gottlieb Steen & Hamilton in Europe.

And while Intel chips are in a majority of all computers, it has a rival, Advanced Micro Devices, and allegations that the chipmaker engaged in predatory pricing in Europe are far different from the issue Microsoft is facing over bundling its Media Player and the interoperability of its server protocols, said Dolmans.

Nonetheless, antitrust attorneys say the decision will be closely watched by a number of parties, from high tech companies to the legal community to other antitrust agencies around the world.

"As a practical matter, I think a lot of the smaller competition jurisdictions will put a lot of weight behind what the Court of First Instance does," said Chris Compton, an antitrust attorney with Wilson Sonsini Goodrich & Rosati. "Korea and Japan may either feel embolden to take action against companies like Microsoft or Intel, or it will constrain them."

As a result, Compton noted, the decision by the Court of First Instance is expected to the most closely watched antitrust decision on a global scale.

"This is a decision," said Compton, "that will have hundreds, if not thousands, of lawyers who'll want to take it apart."