Windows Media

Then there's the DRM built into the latest version of Microsoft's Windows Media platform, which was also significantly updated for Vista -- although for the time being, it remains interoperable with earlier versions of the Windows Media platform and associated DRM technologies, known as WMDRM. The key here, according to Bill Rosenblatt, founder of GiantSteps Media Technology Strategies and managing editor of Jupiter Media's "DRM Watch" newsletter, is the widespread use of WMDRM as a de facto digital music DRM standard.

Rosenblatt noted that besides serving as the underlying content-protection technology for almost every digital music service except for Apple's iTunes Music Store, WMDRM offers a fair amount of interoperability between digital music and portable music players labeled with the Microsoft-sponsored "PlaysForSure" moniker.

"Microsoft has developed an ecosystem of device makers around WMDRM 10," the version introduced with Windows XP, he said. "As a result, the Windows platform has developed a certain amount of interoperability" between music services such as Napster and MusicMatch on the one hand, and hardware manufacturers on the other.

Yet, according to Rosenblatt, there is trouble in paradise -- at least Microsoft's "PlaysForSure" partners are likely to see it that way.