If you want to back em up on a DVD, u need a DVD burner. So forget that, unles ur gonna go out and by a DVD burner. BTW DVDs (4.7Gbs) only fit around 4.4Gbs of raw data
I'd do what Hobbes said, put all ur music on a normal CD, as data. Like this u can fit 700MB music per CD. Thats about 7-8 CDs.
Anyways the Partition Magic would prob take just as long, anyways then there might be som complications...
Edit: Do you have another PC, where you could temporarily save the 5Gbs of Music on?