The U.S. Supreme Court on Monday left standing a lower court's ruling that business software vendor Novell can proceed with an antitrust lawsuit against Microsoft.

Microsoft had sought to appeal the lower court's decision to the nation's highest court, but the jurists declined to hear the case. Supreme Court Chief Justice John Roberts recused himself from the decision because he owns Microsoft stock.

The Supreme Court typically does not state its reasons for declining to hear a case.

Novell sued Microsoft in 2004, claiming the software maker "deliberately targeted and destroyed" its WordPerfect word processor and Quattro spreadsheet franchises because they are compatible with non-Windows operating systems.

Novell sold WordPerfect and Quattro to Corel in 1996. The programs have become relatively obscure in the wake of Microsoft's dominance of the desktop applications market.

Last year, the U.S. Court of Appeals for the Fourth Circuit upheld a district court's ruling that Novell's lawsuit could proceed. The Supreme Court's refusal to hear an appeal of the Circuit Court's decision effectively means the case will go trial unless the two companies reach a settlement.

A settlement is not out of the question.

Microsoft and Novell have become software market allies in recent years. In 2006, the two vendors forged a partnership under which Microsoft resells Novell's SUSE Linux software and services.

Novell and Microsoft also worked out a $536 million settlement in 2004 to resolve Novell's claim that Microsoft plotted to ruin the market for the Novell NetWare operating system.

Microsoft continues to suffer monopoly-related legal problems on other fronts.

The European Union's competition watchdog last month slapped the company with a record $1.35 billion antitrust fine. The European Commission said it imposed the fine after determining that Microsoft isn't living up to the terms of a 2004 antitrust order that compels Microsoft to make its products more interoperable with those made by rivals.

The fine was in addition to the more than $1 billion in penalties the EU originally imposed on Microsoft following the 2004 order.