THIS FALL'S BIGGEST HIGH-TECH battle pits two unlikely opponents: Apple and Napster. The Apple iTunes Music Store now faces competition from a relaunched, legal Napster service.

Many hope online music sales will push pirate file traders back to the margins of cyberspace. Apple boasted that iTunes users downloaded over 1 million songs in the first 35 days after the Windows version debuted.

Meanwhile, Napster's new owners want to leverage the biggest name in music downloading. The new Napster 2.0 service replaces the old MP3-trading network with new pay-to-play song sales. Only the logo remains the same.

Both services offer similar features. Users buy songs for 99 cents and copy them to a portable player or a CD. Competitors like MusicMatch, BuyMusic.com, Rhapsody, MusicNow, and MusicNet all offer variations on this model.

Napster 2.0 and iTunes may wind up playing "good cop" to the music industry "bad cop." Last month, the Recording Industry Association of America sent new legal threats to over 200 people suspected of illegally pirating music online. The group said they were sharing an average of more than 1,000 songs on their computers.