First of all, you need to get the digital music into the computer. If the music is on an audio CD, you can use a program such as AudioGrabber to copy the file (as a .wav file) onto your PC. You then need a program to convert the .wav file into a .mp3 file. (you can do this via a 'music editor', described below, or you can use BladeEncoder, a free encoder, of which I've saved a copy at http://www.ceder.net/csds/ftp/BladeEnc091.zip

If the music is on vinyl, you'll have to get a 'music editor' program (see http://www.ceder.net/digital_music.php ), hook up your turntable/amplifier to the computer, and record the music. You can then save the file as a .mp3 file.