A federal judge said Friday that consumers may go ahead with a class action lawsuit against Microsoft over the way it advertised computers loaded with Windows XP as capable of running the Vista operating system.

The lawsuit said Microsoft's labeling of some PCs as "Windows Vista Capable" was misleading because many of those computers were not powerful enough to run all of Vista's features, including the much-touted "Aero" user interface.

U.S. District Judge Marsha Pechman certified the class action suit but whittled down its scope to focus primarily on whether Microsoft's "Vista Capable" labels created artificial demand for computers during the 2006 holiday shopping season, and inflated prices for computers that couldn't be upgraded to the full-featured version of Vista, which was released at the end of January 2007.

Neither of the two people who filed the original lawsuit participated in a program Microsoft devised to help people who bought new computers before Vista's launch upgrade later to the new operating system, but they argued nonetheless that people who bought "Vista Capable" computers were harmed because they could only run a basic version of Vista.

The judge said if they added a named plaintiff who did take part in Microsoft's "Express Upgrade" program, they could pursue that claim as well.

Microsoft said it was reviewing the ruling.