Of course, those unlimited downloads for a monthly payment come with at least one string attached. Most subscription services, including Best Buy-owned Napster, employ digital rights management technology that requires you to keep your subscription current in order to keep the music playing. Cancel your subscription and all those tracks you downloaded suddenly go silent.

Needless to say, it’s the DRM wrapping that comes with subscription tracks that keeps the downloads from playing on the world’s most popular personal player – Apple’s iPod.

Napster’s new $5 subscription, which launches tonight, doesn’t deep-six the DRM, but it does have an added feature that will make some songs compatible with iPods. That’s right. Some songs will play on iPods, but not all songs. Or even most of them.

Confused? Here’s the game plan.

The new subscription lets you stream tracks from Napster’s 7 million song catalog, listen to more 60 commercial-free radio stations and more than 1,400 “expertly programmed” playlists. Of course, streaming means just that. You can listen to the tracks, but you can’t take them with you.

However, the new subscription also gives you five, DRM-free downloads that will play on just about any personal player, iPod and iPhone included. That’s five songs for five bucks per month. Did that catch your interest?

“There’s no need to settle for 30-second clips to decide if you want to buy a song,” said Napster CEO Chris Gorog. “For five bucks now you can have access to our entire music catalog and get five MP3s to add to your permanent collection.”

Click here for the Napster Web site.