FYI.
Apple's IPOD is the most popular. And probably the best (legal) service. But take this into consideration:
Some models of the IPOD hold up tp 10,000 songs. At a buck each, you'll eventually need a mortgage.
Napster now offers unlimited downoads for $14.95 monthly. 30 day free trial.
I don't know all the specs, but I do know, it's not going to be cheap. 15 song CD's are $12-15 at retail. With the download services, you buy only the songs you want and not the whole CD's. Better deal. You're not stuck with crap you don't like or will never listen to.
Hope that helps.