Media giant AOL Time Warner will continue its own anti-monopoly action against Microsoft, as will Sun Microsystems.
Both are urging the nine US states that rejected last year's settlement with the Department of Justice, to appeal against Judge Kollar-Kotelly's ruling.
European Commission competition officials are also expected to decide by the end of the year on the next steps in a four-year investigation into allegations that the software giant abused its dominant market position.
Commenting on last week's ruling, Sun's special counsel, Michael Morris, said: "We will continue to pursue our civil case and to co-operate with the European Commission's case against Microsoft to ensure that the company does not continue to use its monopoly position to become the gatekeeper of the Internet."
Morris said that choice, innovation and competition were the foundation of the technology industry and the ruling "does little to advance these principles or to protect the millions of developers and businesses that want an open marketplace".
AOL Time Warner general counsel Paul Cappuccio said the ruling "made a weak settlement stronger and created some additional protections".
"The court and the Justice Department have pledged to monitor Microsoft's compliance with the terms of the judgment, and this should have some deterrent impact on its anti-competitive activity," he added.
European antitrust officials are investigating whether Microsoft abused its monopoly power in the server software market. They are also examining whether Microsoft abused its power against RealNetworks' media player and Apple's QuickTime video-player.
Microsoft has made it clear that it would strenuously fight any proposals for the removal of Microsoft's media player software from Windows.