If it is a CD, you will need a CD Ripper . Next you need an MP3 encoder to convert the WAV file created by a ripper or other source into an MP3 formated file. You need a CD Ripper . Finally, you run a MP3 encoder over the WAV file to convert it into MP3 format. The critical point in the process is to rip the files from cd digitally and not using analog methods.
Rippers are digital.
Try not to connect the audio out of your cd player into the IN line on your sound card or lots of sound quality is lost in the analog to digital conversion. Some rippers wont support your digital cd to sound card connection, and linein is your only choice. To check if your CD is capable of digital ripping, try this page for a list of known compatible drives. Normally, its where a microphone is plugged into your sound card. Next, fire up a good recorder program on your platform.