Greendog, the fact you have music on your PC means it has already been 'ripped'. i.e extracted from a CD to your PC's hard-drive. The files you have may well be in the Wav format or similar.
What you probably need to do is convert the audio tracks on your hard-drive to mp3, so that they can be played on you mp3 player.
This program may be just the tool you need.;
http://www.dbpoweramp.com/dmc.htm
It will convert all sound file types to other formats, including mp3.
Hope this helps.