Microsoft says the European Union is about to levy what the company calls an unreasonable fine on the software giant in an anti-trust case.
News reports say EU officials on Wednesday will order Microsoft to pay more than $600 million, and change the way it sells software. Microsoft has vowed to appeal any negative decision in court.
Microsoft is the world's largest software company, and its Windows operating system runs basic functions on 90 percent of all desktop computers.
Critics say Microsoft is abusing its dominant position by closely weaving new audio-visual software into the operating system, making it unfairly difficult for rival software companies to compete.
Microsoft says it should not pay a fine because the European Union calls this a "precedent-setting case" so the company could not know its actions were illegal under EU law. The company also argues that if any EU fine is levied, it should be based on a percentage of its European sales, not its global operations.
Some information for this report provided by Reuters, AP and AFP.