In a ruling issued this afternoon, U.S. District Judge Marsha Pechman reversed her earlier decision granting class-action status to the lawsuit over Microsoft's Windows Vista Capable marketing program. However, Pechman denied Microsoft's motion for summary judgment, saying PC buyers could pursue their claims individually. Here's the ruling: PDF, 17 pages.

Barring appeal, the ruling appears to steal most of the thunder from the lawsuit, because individual plaintiffs aren't as likely to pursue cases against Microsoft on their own. I've left a message for the plaintiffs' lawyers to find out what they plan to do next. [Update 5 p.m.: Plaintiffs' lawyer Jeff Thomas says they're reviewing the ruling and considering their options. He declined to comment further for now.]

According to today's ruling, Pechman removed the class-action status after finding that the plaintiffs hadn't adequately shown that the Vista Capable program caused widespread, artificial inflation in PC prices. However, she said, that doesn't preclude specific plaintiffs from pursuing claims against Microsoft if they can provide "evidence of individual deception."

Microsoft spokesman David Bowermaster said in a statement: "We're pleased that the court granted our motion to decertify the class, leaving only the claims of six individuals. We look forward to presenting our case to the jury, should the plaintiffs elect to pursue their individual claims."

The suit focuses on the months prior to Windows Vista's January 2007 release, when Microsoft and PC makers used the Vista Capable program to assure buyers of Windows XP machines that their new computers would run Vista when it came out.

The plaintiffs alleged that Microsoft wrongly classified as "Vista Capable" computers that could only run Windows Vista Home Basic -- which doesn't include the Aero Glass interface or other "signature" Windows VIsta features. In essence, the suit argues, Home Basic isn't really Vista, and it shouldn't have been touted as Vista in the marketing program.

In response, Microsoft argued that Home Basic was Windows Vista, and was rightfully included in the marketing program.

Pechman offered a different take in her ruling today.

"Simply put, Microsoft’s argument misses the issue," she wrote. "The question is not whether Basic can be called 'Vista' based on computer code similarity or whether Microsoft as a software developer has the right to offer multiple permutations of its product; it is whether Microsoft’s use of the “Vista Capable” designation had the capacity to deceive."

Explaining why she would let individual PC users pursue claims against the company, Pechman wrote that "Microsoft’s internal communications raise a serious question about whether customers were likely to be deceived by the WVC campaign."

That was a reference to internal emails such as one in which former Windows chief Jim Allchin wrote, "I believe we are going to be misleading customers with the Capable Program. OEMs will say a machine is Capable and customers will believe that it will run core Vista features."

The Windows Vista Capable case has resulted in the disclosure of a series of internal emails showing Microsoft executives complaining privately about Windows Vista, bowing to pressure from Intel to lower the requirements for the "Vista Capable" logo, and getting into hot water with H-P and others. See this earlier story for background.