The lawsuit over Microsoft's Windows Vista Capable marketing program has long been a thorn in the company's side -- bringing to light large batches of emails revealing the internal turmoil that accompanied the operating system's development and release. Now, after winning a key court ruling last month, the company is trying to keep the class action from coming back to life.

In its latest court filing (PDF, 27 pages), Microsoft asks the judge to reject the plaintiffs' bid to regrant case class-action status to the case. The company argues that PC buyers would need to be quizzed individually to see if they were misled by the Vista Capable marketing program. Microsoft says that rules out a class action, in which a handful of plaintiffs would represent the experiences of the larger group.

The "Windows Vista Capable" program was used by Microsoft and PC makers in late 2006 to assure computer buyers that the Windows XP machines they were buying would run Windows Vista when it came out in January 2007. The plaintiffs allege that the marketing program wrongly classified as "Vista Capable" computers that couldn't run Aero Glass and other "signature" Vista features.

After U.S. District Judge Marsha Pechman removed the initial class-action status from the case, the plaintiffs' lawyers asked the judge to regrant that status based on narrower groups of plaintiffs: People who bought PCs through Microsoft's Express Upgrade Guarantee Program, and those who bought PCs that didn't support Windows Vista's advanced graphics.

In its latest filing, submitted earlier this week, Microsoft says the plaintiffs are ignoring "the critical fact that many customers knew which edition of Windows Vista they would receive through that program (and what features of Windows Vista that edition would provide) and thus received what they expected."

Apart from that, the company argues that plaintiffs are too late with their request to certify a narrower class. The judge, the company says, "should decline to entertain Plaintiffs belated request for certification on theories known to them for more than a year."

The case is currently scheduled for trial April 13. However, because the judge removed the class-action status, it would involve only a handful of plaintiffs, unless something changes in the meantime. The plaintiffs have asked the judge to push back the trial to allow time consider its motion to certify a narrower class. The judge has yet to rule on that request.