Napster announced on Sunday that starting with spring it would begin selling music downloads as unprotected MP3 files. Thus, Napster, which is one of the largest digital music retailers, joins some other companies that have already decided to sell songs as MP3s.

In the past, Napster had sold songs protected with Microsoft’s Windows-based DRM (digital rights management) system, which prevented users from illegally making multiple copies or distributing music tracks to other people.

In fact, Napster has always liked MP3s. The company became popular in the 1990s as the first major free marketplace for DRM-free music tracks in the MP3 format. But at the time, Napster was an illegal service for users to share their music files; in the end the company was sued and closed by the music industry in 2001. Now, with the use of DRM becoming so controversial and eventually unpopular, Napster felt its time has finally come.

The digital rights management system has started to frustrate people when they began to find out that songs they had bought can only be played on certain compatible digital music players or could not be moved from one PC to another. Major music companies such as EMI Group, Universal Music Group and even Warner Music Group have recently started selling music tracks in the MP3 format, which is still the most widely available digital audio format and plays on the widest range of devices.

"We projected a year ago that there would be a critical mass of support for MP3, and we're pleased to see the music industry is beginning to support it," said Chris Gorog, Napster’s Chief Executive. "There's now enough top-tier content out there."