BRUSSELS (Reuters) - Microsoft <MSFT.O> said on Friday it was appealing against a record 899 million euro ($1.39 billion) fine imposed by the European Commission for using high prices to discourage software competition.

"Microsoft today filed to the (EU) Court of First Instance an application to annul the European Commission decision of February 27," the U.S. software giant said in a statement.

"We are filing this appeal in a constructive effort to seek clarity from the court," it said.

The European Union's executive Commission, which has been locked in a long-running battle over fair-competition issues with Microsoft, said in response that it was confident the fine was "legally sound."

The Commission had said it was imposing the fine because the U.S. software group had defied a 2004 order from Brussels to provide information to competitors on reasonable terms.

Microsoft has been fined a total of 1.68 billion euros by the EU for abusing its 95 percent dominance of PC operating systems through its Windows operating system.

The 899 million euro fine was the biggest ever imposed on a company by the EU executive.

The Commission had initially fined Microsoft 497 million euros in March 2004 for withholding interoperability information for "work group server" software and for deliberately damaging rivals by tying its Windows Media Player to its Windows system.

Microsoft unsuccessfully appealed against that penalty and was also later fined 280.5 million euros by the Commission for non-compliance.

The latest fine picked up from where the 280.5 million euro penalty left off, covering the period from June 21, 2006 until October 21, 2007.

(Reporting by David Lawsky, writing by Darren Ennis, editing by

Dale Hudson)