They said the expanded probe began last month when the Fair Trade Commission received a complaint from RealNetworks, a US firm marketing the "RealPlayer" audio-visual software, that Microsoft violates anti-trust laws.

RealNetworks accused Microsoft and its South Korean unit of unfairly bundling the "Media Player" program and the "Media Server" program with its Windows operating system, according to the commission.

Microsoft has been the subject of a seperate probe by the commission since South Korea's largest Internet portal Daum Communications filed a complaint in September 2001.

Daum, which has its own messaging service, said Microsoft violated anti-trust rules by unfairly incorporating its "MSN" instant messaging software into its Windows system.

Microsoft is engaged in a legal battle with the European Commission, which ruled in March that the US company should sell its Windows system without its Media Player software for fair competition with European rivals.

The Brussels commission also fined Microsoft nearly half a billion euros (dollars).

Microsoft has appealed the European Commission ruling.

All rights reserved. copyright 2018 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.