Yahoo has become the latest company to abandon customers who bought tracks from its music store encoded with DRM (digital rights management), drawing fire from the Electronic Frontier Foundation (EFF).

On Sept. 30, Yahoo will shut down the servers that are needed to reauthorize music purchased from its failed Unlimited Music Store if it is transferred to a new PC, Yahoo said in an e-mail to customers. The rule is designed to slow music piracy. Re-authorization is also needed if someone upgrades their PC's operating system.

The only workaround for customers wanting to listen to their music on a new or upgraded computer after this date is to burn the tracks to a CD and then reload them on a PC.

Those with extensive music collections would incur the cost of buying blank CDs and spending time to transfer the music, wrote EFF staff attorney Corynne McSherry in a blog post.

Even though Yahoo suggested that process to customers to preserve their music, it raises legal issues.

"This suggestion could put customers at legal risk, as they may not have documentation of purchase," McSherry wrote. "Furthermore, there is no certainty that all relevant copyright owners would agree that making such backup copies without permission is lawful."

The EFF has warned for years about the consquences for consumers when vendors decide to withdraw their support for DRM-encoded music, McSherry wrote. Over the last year or so, an increasing number of online music vendors, in cooperation with major music labels, are offering tracks minus DRM after failing to dent piracy.

Yahoo said in February it would shut down its Unlimited Music Store after partnering with RealNetwork's Rhapsody service. Last month, Rhapsody said it will sell unrestricted MP3 files, following Apple's move to offer DRM-free tracks in its iTunes Music Store.

The EFF is pushing Yahoo to offer a refund for the affected tracks or provide replacement tracks without DRM along with receipts to prove the music has been legally purchased in the event of a copyright-infringement lawsuit, McSherry wrote.

Last month Microsoft reversed course after intially saying it would stop reauthorizing music bought from its shuttered MSN Music service on Aug. 31. The company committed to reauthenticating tracks through 2011.

Tracks sold in the Microsoft and Yahoo music stores used the Microsoft's PlaysForSure DRM, now vaguely named "Certified for Windows Vista."