Monday, February 28, 2005; 8:53 AM

ITunes: Spurred by the runaway popularity of the iPod player, Apple`s iTunes has grown to become the nation`s most successful download store, selling more than 250 million tracks -- typically for 99 cents each -- since its launch in 2003.

RealNetworks: Best known for its ubiquitous ``RealPlayer,`` the company offers one-song-at-a-time downloads as well as $10 monthly subscriptions to the unlimited-download Rhapsody service.

Napster: Named for the underground file-swapping service that started it all, the reborn Napster offers a subscription similar to Rhapsody, with a ``To Go`` service allowing transfers to approved portable players for an additional $5 a month.

MusicMatch: Owned by Yahoo, MusicMatch offers a range of services including a la carte downloads, Web radio and a subscription service.

MusicNet: Unlike its peers, MusicNet doesn`t operate a retail store. Instead it provides the back-end download technology for companies like America Online and Virgin Digital.

Wal-Mart: The retail giant sells a la carte downloads at 88 cents a song.

Buy.com: The Internet retailer offers 79-cent singles from major-label artists.

MP3tunes.com: Launched by the founder of the now-defunct MP3.com downloading site, the service offers 88-cent downloads of songs from independent artists.

Emusic: This smaller service specializes in independent labels, offering bulk downloads for a monthly fee.

Peer Impact: Still in its testing phase, Peer Impact would allow users to share files while digital rights management technology automatically determines what fees they owe.

Ruckus Network: Ruckus specializes in the college market, offering music and movie downloads through arrangements with universities.

Cdigix: Another company specializing in the college market, Cdigix uses MusicNet`s technology.

--David McGuire