Microsoft will head to US federal court today to battle an antitrust lawsuit filed by rival Sun Microsystems.
Having won court endorsement of an antitrust settlement with the federal government and a group of states, lawyers for Microsoft are due to present arguments against Sun, which has asked a federal judge to force Microsoft to include Sun's Java programming language in the Windows XP operating system.
Sun's antitrust lawsuit is one of several before US District Judge J. Frederick Motz in Baltimore - filed in the wake of Microsoft's long-running antitrust fight with the government.
He is also overseeing cases filed by AOL Time Warner unit Netscape Communications, Be Inc. and Burst.com, as well as class-action attorneys suing on behalf of consumers.
Sun filed its antitrust lawsuit in March, after a federal appeals court upheld a lower court ruling that Microsoft had broken US antitrust laws and illegally maintained its monopoly over personal computer operating systems.
Sun is seeking more than $1 billion in damages, claiming Microsoft impeded the use of its Java software platform.
Microsoft dropped Java from the operating system when it introduced Windows XP last year. It later reversed itself and said it would start including Java in an update of Windows XP, but only until 2004.
Microsoft said it was forced to drop Java because of legal problems stemming from another lawsuit that Sun had filed against the company.