A US federal judge has given the official go-ahead for a class action lawsuit against Microsoft, claiming that the software giant's "Vista Capable" scheme deliberately misled consumers.

Two plaintiffs are suing Microsoft in a Seattle court stating that the "Windows Vista Capable" stickers added to PCs at the end of 2006, before the new operating system was launched, were a lie.

The argument is that the stickers appeared to suggest that the PCs could run any version of Vista, but in fact it was only a guarantee to run Vista Home Basic, not "real" Vista.

During the hearing, the judge was shown emails from Microsoft employees that expressed serious doubts about the scheme, including one that stated "even a piece of junk will qualify" for the sticker.

Microsoft has declined to comment.