Microsoft’s decision to effectively switch off the tracks purchased by customers using its now defunct MSN Music service has landed the company with a hail of criticism.

Microsoft last week told former MSN Music customers that it would no longer support the DRM licenses for tracks bought through the failed music sales portal. The news meant customers would lose the ability to play the music they own once their existing computers ceased to function.

The company’s decision has attracted the ire of digital lobbying group the EFF, founded by former Grateful Dead lyricist John Perry Barlow.

In a letter to Microsoft CEO Steve Ballmer, EFF said: “While this announcement has directly affected MSN Music customers, users of other Microsoft products (particularly current and prospective Zune customers) are deeply concerned as well. Your customers are forced to ask, "If Microsoft treats its MSN Music customers so shabbily, is there any reason to suppose that it will treat other customers any better?" the EFF thundered.

The EFF is demanding Microsoft issue and apology and a refund to its customers. It also insists the company should “Ensure that all MSN Music buyers have (or have permanent access to) receipts identifying dates, amounts, and titles purchased, so they have proofs of purchase,: in case of any future problems proving they own their tracks. EFF also wants Microsoft to work to eliminate DRM from the Zune music catalogue in order to ensure customers don’t have to suffer such inconvenience and loss again.

Microsoft has said customers should back up their music libraries by burning them to CDs. "There is no certainty that all relevant copyright owners would agree that making such backup copies without permission is lawful," responds the EFF.