if you are looking for your first music/media player, you might check out the poll in here about them. the thread is listed under "media player" dated this month.

once you "rip" a song it goes to your music file, that's where you can customize your files.
some media players have preferences you can set to accept or play different file extensions.
i think windows media player is limited on what it will accept. i-tunes will convert files when you import to library and converts for i-pod. when you import to realplayer you can still see the original file ext. it converts (mine) to mp3 at 192 kbs, when you burn a cd. i have yet to find an ext that "realplayer" doesn't play. i use i-tunes now but still learning.

realplayer.com & rhapsody.com have free trials. i'm sure there are other free media players out there.