Microsoft seems in the frame for another investigation by the European Commission, following a complaint from Opera Software.

The web browser publisher has complained that Microsoft is abusing its dominant market position by tying its browser, Internet Explorer, to the Windows operating system and by hindering interoperability by not following accepted web standards.

Microsoft - already convicted of abusing its dominance by European and US regulators - is accused of denying customers a genuine choice between browsers.

Opera has requested the Commission act to compel Microsoft to give consumers a real choice and to support open standards.

"We are filing this complaint on behalf of all consumers who are tired of having a monopolist make choices for them," said Jon von Tetzchner, CEO of Opera. "In addition to promoting the free choice of individual consumers, we are a champion of open web standards and cross-platform innovation. We cannot rest until we've brought fair and equitable options to consumers worldwide."

Opera Software wants European regulators to force Microsoft to unbundle Internet Explorer from Windows and/or to carry alternative browsers pre-installed on the Windows desktop.

It also asks that the European Commission requires Microsoft to follow fundamental and open web standards, rather than being allowed to continue its long-established, "embrace and extend" strategy to undermine of control them.

Microsoft's unilateral control over standards in some markets creates a de facto standard that is more costly to support, harder to maintain, and technologically inferior - and can exposes users to security risks.

"Our complaint is necessary to get Microsoft to amend its practices," said Jason Hoida, deputy general counsel, Opera." The European Court of First Instance confirmed in September that Microsoft has illegally tied Windows Media Player to Windows.

"We are simply asking the Commission to apply these same, clear principles to the Internet Explorer tie, a tie that has even more profound effects on consumers and innovation. We are confident that the Commission understands the significance of the Internet Explorer tie and will take the necessary actions to restore competition and consumer choice in the browser market."

As a result of its dominant marketshare - itself built through years of proven anti-competitive company strategies - Microsoft has locked consumers to its own browser.

Opera believes that the remedies will help promote consumer rights worldwide and force Microsoft to begin competing with Opera and others on the merits of its browser.