Microsoft competitors are concerned the European Union may not prevent future antitrust abuses by the software giant, as the EU reaches the closing stages of its antitrust investigation into the company.

A central issue in the case concerns Microsoft bundling its Media Player in the Windows operating system. The Commission believes this form of bundling gives Media Player an unfair advantage over competitors. Microsoft has said it's unwilling to take the video and audio player out of Windows.

Microsoft competitors want the European competition regulator to word its ruling in such a way that it applies to the bundling of other middleware products.

"If the EC rules that Microsoft should unbundle Media Player, I don't see Microsoft voluntarily unbundling other middleware from the operating system," said Thomas Vinje, a lawyer at Morrison & Foerster, which has represented some Microsoft competitors.

The Commission might tightly word its ruling to avoid any potential appeal by Microsoft, he said.

"If they do that, we will have to file new complaints about other products bundled into Microsoft's operating system," Vinje said, adding "in which case it begs the question whether competition law is relevant to such a fast-moving industry".

Other industry sources have also questioned the real impact a European ruling against Microsoft would have.

"If they tackle the problems product by product, then Microsoft will in the future weigh up the potential antitrust fines against sales, and they'll probably decide it's worth bundling products into Windows because it takes the Commission so long to react," said one person from a rival company who requested anonymity.

Toward the end of last year, the Commission said it would consider another settlement offer from Microsoft before closing the case. Microsoft is believed to be close to submitting such an offer, though neither party would comment.

The EU case has focused on whether Microsoft uses its dominance in operating systems to thwart competition in related markets. It relates to complaints regarding the company's activities in the server and operating system markets.