Most of the available space on the hard drive is taken up by the navigation portion of the system. Kind of deceptive isn't it?
If you can, rip them to your computer first and then copy them to flash drive to copy over to the Challenger. I copied one CD in my Challenger and it took easily 2-3 times longer than copying off the flash drive."30 GB" is misleading, but 16 GB is still a ton of music to have on hand without messing with CDs. It is quite easy to erase songs from CDs you have copied, or entire CDs. Just go to the "manage HDD" menu. My beef is that the hard drive inserts a second of silence between tracks, very irritating if they're supposed to blend together, or you're listening to a live concert with crowd noise.