Great News... and now if you want to investigate the many ways to compress files, then that would be a nice topic for this board to explore.
We just need to identify file types (text, music, etc) and which compression tools work on each, and what the trade-offs are for music files.
Most likely we could compress the 4-5 GBs on your harddrive to fit onto a single CD, or maybe better if you can group certain albrums together and do a less-lost compression and make 2 or 3 CDs.