People who bought songs from Microsoft's now-defunct MSN Music service will get three more years to move the music to new devices and operating systems after a change of course by the company.

Microsoft said it will now support authenticating those tracks, as required by the DRM (digital rights management) technology encoded into the music, through at least the end of 2011. Microsoft will then decide based on demand whether to continue.

Songs purchased on the service, offered only in the U.S., used Microsoft's "PlaysForSure" DRM, which required that the songs gain a license key from Microsoft's servers if a user transferred the music to a new PC or device.

But MSN Music, one of several online music store efforts by Microsoft, was shut down in November 2006 when the company launched a new one centered around its Zune digital music player.

Then Microsoft said in April that it would only support authenticating songs from MSN Music through Aug. 31. The decision meant that users could no longer migrate their music to a new PC if they upgraded their hardware.

If a person's PC died, the music would be gone unless it has been backed up on a CD or to another hard drive. Even if a user merely upgraded their operating system, for example from Windows XP to Vista, authentication is still required.

Microsoft's decision drew fire from users and organizations such as the Electronic Frontier Foundation, which said consumers should be entitled to refunds.

PlaysForSure DRM, which Microsoft has renamed "Certified for Windows Vista" has a set of Byzantine rules for how content can be burned to CDs and shared with other devices.

The Zune Marketplace sells songs using Windows Media DRM 10.

Some content is available in unprotected MP3 format as music industry warms to the idea of selling music without DRM after backlash from consumers.

Apple, whose iTunes Music Store remains the most popular place to buy music online, is selling some tracks minus its version of DRM, called FairPlay, after new agreements were reached with music labels. Amazon.com also sells songs from Warner Music Group without DRM in the MP3 format.