Yes but you'll lose quality, and sometimes you can't even do that legally. And even the original music you buy will not be CD-quality. It sounds perfectly fine on your average PC speakers, but as people connect their mp3s up to higher-end speaker systems, they'll notice the lack of quality a bit more.
DRM is digital rights management (sometimes jokingly referred to as digital restrictions management). it's an extra bit of software put onto some music and films etc. designed to prevent you from using things you've bought the way you want to. for example, music bought from the iTunes music store is DRM'd, as is most other legal music. it restricts how you are allowed to listen to your own bought music, supposedly because sharing music is hurting the artists. I thought the whole point of music was for it to be heard -- but maybe not. Either way, it's only hurting one thing: the record industry's execs' pockets.
example of how it's bad: ever heard of PlaysForSure? It's microsoft's version of DRM, on lots of legally bought music. Many mp3 players like the Creative models carry the logo, so you know you can buy that music and it'll "play for sure". also know that microsoft is releasing their own zune music player? Guess what? It's not compatible with PlaysForSure. it uses an entirely different DRM system. anyone who's previously bought PlaysForSure music will have to re-buy all their music if they want it on their zune. nobody's under any obligation to keep supporting the PlaysForSure system. If everyone just stopped making devices that play it (one day they will), your music will just stop playing. the end.