Norwegian Web browser maker Opera on Thursday filed an antitrust complaint against Microsoft in Europe, accusing the software giant of illegally using its dominance in the computer operating system market to monopolize Internet technology.

In a complaint filed with the European Commission, Opera claims that Microsoft's bundling of its Internet Explorer browser with the Windows OS makes it difficult for third-party browser manufacturers to compete and limits consumers' buying options.

"We are filing this complaint on behalf of all consumers who are tired of having a monopolist make choices for them," Opera CEO Jon von Tetzchner said in a statement.

Microsoft denied that it's restricting choice in the browser market.

"It's important to note that computer users have complete freedom of choice to use and set as default any browser they wish, including Opera, and PC manufacturers can also pre-install any browser as the default on any Windows machine they sell," Microsoft said in a statement. Opera also accused Microsoft of bolstering its dominance of the browser market by employing non-standard technologies that don't interoperate with products from third parties.

To remedy the situation, Opera is asking the EC to order Microsoft to sell a version of Windows that doesn't come with Explorer pre-installed. It also wants the commission to order Microsoft to use "open Web standards" in its Internet software.

The requests aren't without precedent. The EC last year forced Microsoft to detach its Windows Media Player software from Windows Vista in the wake of complaints from makers of rival digital media software. The result was a version of the OS called Windows Vista N that sells in Europe.

"We are asking the commission to apply these same, clear principals to the Internet Explorer tie," Opera deputy counsel Jason Hoida said in a statement.

Opera's complaint marks the latest round of legal troubles for Microsoft in Europe. In September, the continent's second highest court upheld $1 billion in Windows-related antitrust penalties against the software maker.

The EC, however, has had only limited success in its efforts to legislate competition in the software market. Microsoft has reported that sales of Windows Vista N have been negligible, and that most European consumers have overwhelmingly chosen to buy the full version of Vista.