SEATTLE (AP) – A lawsuit claiming people were fleeced by the way Microsoft Corp. advertised some Windows XP computers as capable of running the new Vista operating system is no longer a class action, a federal judge has ruled.

The lawsuit, certified last February as a class action, argued that Microsoft’s designation of some PCs as “Windows Vista Capable” was misleading because many of those computers were not powerful enough to support all of Vista’s features, including the sleeker “Aero” user interface.

U.S. District Court Judge Marsha Pechman reversed course and decertified the class late Wednesday. In her decision, she wrote that the people who brought the lawsuit did not prove Microsoft artificially inflated demand for PCs that could run only the stripped-down version of Vista.

They also failed to prove Microsoft was unjustly enriched by sales of “Vista Capable” computers, Pechman wrote.

The judge did leave the door open for individuals to pursue similar lawsuits against Microsoft, however.

Over the last year, the case has made public reams of e-mails between Microsoft, PC makers and chipmakers that show top executives questioning Microsoft’s marketing plan for the months preceding Vista’s January 2007 launch. In part to keep PC demand from dropping off during the important holiday season, Microsoft and computer makers stuck the “Vista Capable” labels on some computers, while marking other, more powerful machines as “Premium Ready,” or able to run a full-fledged version of Vista.

Some e-mails also indicated Microsoft lowered its standards for “Vista Capable” computers to include a certain line of Intel Corp. chips.

While Pechman did not find enough support for the class action suit, she didn’t indulge Microsoft’s request to end the matter with a ruling in its favor. She wrote that the e-mails raised enough questions about Microsoft’s marketing decisions – and their potential to deceive shoppers – to leave individuals the option to sue.

Microsoft shares were down 16 cents at $17.96 in afternoon trading.

Copyright 2009 The Associated Press.