If you make unauthorized copies of copyrighted music recordings, you're stealing. You're breaking the law and you could be held legally liable for thousands of dollars in damages.
Hm. Nope. Not illegal to make copies for personal use. That's pretty much been the backbone of all the related lawsuits so far, that it is fine to make copies for your own use, you just aren't supposed to share them with others or (more importantly) profit off them.
The RIAA honestly thinks that if you want to listen to a song on your CD player, your computer and your mp3 player, that you should pay for it three times.
And they wonder why people are generally pissed off at record companies.