The European Commission has charged Microsoft a second time for abusing its monopoly of the software market.
This time the EC is tackling Microsoft over tying Internet Explorer to the Windows operating system.
US authorities filed similar charges against Microsoft in 1998, but by 2000 had failed to force a separation of the two.
In 2004, the EC was successful in its monopoly abuse case against Microsoft for linking its media player to Windows, fining the software-maker Euro497m.
The latest EC charges follow a year-long investigation in response to a complaint by Norwegian browser development firm Opera Software.
In its December 2007 complaint, Opera called on the EC to compel Microsoft to give consumers a real choice of browser.
Opera also complained that Microsoft was hindering interoperability by not following accepted web standards.
Jason Hoida, deputy general counsel for Opera, said he was confident the EC would take all necessary actions to restore competition and consumer choice.
Microsoft could come under increased pressure in the US with a change in administration, which may not be as corporate-friendly as the previous one.
The likelihood of anti-monopoly charges against Microsoft is also increased by the fact that the company has integrated more internet capabilities into Windows 7, the next version of its operating system.