I think the only way you can do it is if you change the cd files (which are usualy WAV or WMA) into mp3 files you can fit loads more onto a std cd theres a program called freerip which is a free file converision program the only drawback is you need to make sure your head unit is mp3 compatible, the other choice is by an mp3 modulator you plug it into you pc's usb download your songs then plug it into your ciggy lighter, find a free fm station on your head unit & tune it till it picks up your songs of the modulator a play them through your cars audio system.