Oslo (Norway) - Niche Internet browser company Opera has filed a complaint against Microsoft, alleging its tie-in of Internet Explorer into Windows violates European Union guidelines.

Opera says Microsoft needs to give users a choice of what Internet software to use with Windows, and that by failing to do so it is "not following accepted Web standards."

This may result in an investigation by the European Union, a situation all too familiar for Microsoft. The software giant has been fined millions of dollars from the regulatory organization.

Microsoft responded to Opera’s claims by saying, "We will, of course, cooperate with any inquiries into these issues, but we believe the inclusion of the browser into the operating system benefits consumers, and that consumers and PC manufacturers already are free to choose any browsers they wish."

Opera has failed to grab a steady footing in the computer browser market, but has found some success in creating specialized Web browsers for cell phones, the Nintendo DS and the Nintendo Wii.