Is this the last gasp for the Windows Vista Capable lawsuit? A federal judge this afternoon gave Microsoft a key victory in a case best known for disclosing internal company emails in which executives privately groused about the flagship PC operating system.

U.S. District Judge Marsha Pechman denied an attempt by PC buyers to reinstate class-action status in the lawsuit over the "Vista Capable" marketing program. Pechman wrote in her ruling (PDF, 18 pages) that the allegations raise "a host of individualized questions" that would make it unreasonable to try the case on behalf of a large group of consumers.

Attorneys for the plaintiffs couldn't be reached for comment Friday evening. However, they hinted strongly during an earlier court hearing that they would appeal if their renewed motion for class-action status wasn't successful.

The case targets the marketing program that Microsoft and PC makers rolled out to maintain sales of Windows XP computers during the 2006 holiday season, following the Redmond company's decision to delay Windows Vista's release. Labels assured computer buyers that the PCs they were buying would be "capable" of running Windows Vista when it came out in 2007.

The plaintiffs allege that the "Vista Capable" label was wrongly given to machines that could run only Windows Vista Home Basic. That version of the operating system doesn't include the fancy "Aero Glass" graphics and other features that Microsoft touted in advertisements and other materials about Windows Vista. As a result, the plaintiffs claim Home Basic isn't the "real" Vista.

Microsoft disagrees, and says it made the differences clear as part of the "Vista Capable" program.

The case has brought to light a long list of internal Microsoft emails, some of them contradicting what the company was saying publicly at the time. Most notably, emails between Microsoft CEO Steve Ballmer and others showed that executives were privately complaining about Windows Vista even as the company was touting the operating system's features and capabilities

"I know that I chose my laptop (a SONY TX770P) because it had the Vista logo and was pretty disappointed that it not only wouldn't run Glass, but more importantly wouldn't run Movie Maker," wrote Microsoft executive Mike Nash in one message. "I now have a $2,100 e-mail machine."

Other emails showed Microsoft bowing to pressure from Intel to lower the requirements for the "Vista Capable" logo, and getting into hot water with H-P and others over the way the company handled Vista's development and release.

The judge initially certified the case as a class action, but later removed the class-action status after finding that the plaintiffs hadn't adequately backed up their theory that the Vista Capable program resulted in an artificial inflation in PC prices. Lawyers for the plaintiffs followed up by asking the court to certify two narrower classes of PC buyers -- people who bought those PCs through Microsoft's Express Upgrade Guarantee Program, and those who bought PCs that didn't support Windows Vista's advanced graphics.

In her ruling today, the judge maintained that class-action status isn't appropriate.

"For the purposes of a (Consumer Protection Act) claim, the predominant questions would relate to Plaintiffs’ subjective understanding of the Express Upgrade program and their individual belief in Microsoft’s Vista advertising campaign. Such proof is not amenable to class-wide treatment. Similarly, the proposed class cannot assert an unjust enrichment claim because the trier of fact would have to determine whether Microsoft’s profit was inequitable in light of any actual individual deception."

The effect, absent appeal, would be to narrow the scope of the case from potentially thousands of people to just a handful. In her ruling, the judge told the two sides to meet and decide whether they will proceed to trial over the claims of the six named plaintiffs.