I'd like to back up my iTunes library, which consists mostly of songs that I own on CD and that I transferred manually on iTunes. I'd eventually like to be able to transfer these files from the backup device to another computer (probably a PC laptop). Should I use an iPod (thinking of the new iPod classic, which has a 160 GB memory) or an external drive? Is the fact that most of my music wasn't purchased on iTunes a problem? What about iCloud as an alternative?