The company has been accused of in 2006 using Windows Vista Capable stickers on PCs that would only be capable of running the most rudimentary version of the then-forthcoming OS, Vista Home Basic.
The lawsuit was filed last April in the US District Court for the Western District of Washington.
While certifying the class-action suit, US District Judge Marsha Pechman questioned whether Microsoft created artificial demand for the high-priced computers that could not be upgraded to the full version of Vista.