Adding to the confusion surrounding Microsoft's PlaysForSure DRM campaign, the company has now rebranded the effort "Certified for Windows Vista."

The DRM technology itself is unchanged. It's still the most common technology used by subscription music services to govern music licenses. Tracks downloaded under a subscription plan must be recertified at least once a month to continue playing.

Microsoft first unveiled the PlaysForSure campaign to ease customer's confusion over which devices -- such as MP3 players or in-home network adapters -- were compatible with the various subscription services. The iPod, for instance, is not.

Support for both the campaign, and the technology behind it, sagged once Microsoft launched its Zune device and service. The effort does not use the PlaysForSure technology, causing many to question Microsoft's commitment to supporting a technology used by Zune competitors.

Having spent the last three years training customers to look for the PlaysForSure logo when buying compatible devices, the abrupt switch comes as a bit of a surprise. Microsoft has issued no formal explanation for the move.