A federal judge has granted class-action status to a lawsuit filed by two consumers who claim Microsoft's "Windows Vista Capable" marketing campaign was misleading.

Seattle District Court Judge Marsha Pechman, who last year rejected Microsoft's request for a dismissal of the case, last week effectively expanded the lawsuit to potentially include all consumers who purchased a Windows XP PC advertised as "Vista Capable."

In their initial complaint, consumers Dianne Kelley and Kenneth Hansen claimed they were the victims of "bait and switch" sales tactics by Microsoft and filed a lawsuit against the software maker last March, alleging that the company used deceptive marketing tactics to promote the Windows Vista operating system.

Kelley and Hansen claimed that many personal computers labeled Vista Capable before the OS hit stores a year ago were hardly that. Microsoft assured consumers "that they were purchasing Vista capable machines when, in fact, they could obtain only a stripped down operating system," according to the complaint.

In contention is the very definition of Windows Vista itself. Kelley and Hansen argue that some computers sold as Vista Capable were capable of only running a basic version of the operating system that lacks Vista's defining features -- such as the space-age Aero interface, Flip 3-D navigation tools, and Media PC functions.

On its Web site, Microsoft has stated that the Home Basic edition of Windows Vista must run on a PC that has at least an 800-MHz processor, 512 Mbytes of system memory, and a graphics processor that is Direct X 9 compatible. In contrast, premium editions of the operating system require at least a 1-GHz processor, 1 GB of system memory, and a 40-GB hard drive with 15 GB of free space to run properly.

Microsoft has said its Vista Capable campaign included a Vista Premium Ready marketing effort that clearly stated the differences among the various versions of the operating system and the hardware needed to run them.