Microsoft is appealing against a South Korean ruling that it must unbundle its media player and messaging service from its Windows software system.
Microsoft was accused of "hurting the interest of consumers" in Korea
South Korea's anti-monopoly watchdog, the Korea Fair Trade Commission (KFTC), found against the US giant in December.
Microsoft was also fined 32.5bn won ($33m; £19m) after the KFTC upheld a complaint by Korea's second largest internet firm Daum Communications.
The US firm insists its bundled systems do not harm Korean competition.
It says Korean customers can easily download rival systems.
"Microsoft today filed an appeal with the Seoul High Court to review the decision in the Korea Fair Trade Commission (KFTC) case against Microsoft," Microsoft said in a statement.
The KFTC continued to investigate Microsoft's practices, despite the firm paying Daum $30m in November to end their dispute.
The ruling of the KFTC echoes a similar 2004 judgement by the European Commission, which also found that Microsoft was abusing its market domination.
Microsoft's rivals have since accused the firm of dragging its feet over unbundling its software in Europe, something Microsoft denies.