i've had hard disks fail and i've had dvd's get lost and broken too, so i tend to backup to a second hard drive and also to dvd.
plus i always make sure i put my favs on a usb drive. you can get 4gb really cheap nowadays and that holds a decent quantity of music.
oh and thanks to enemyat_thesix for "the bounce". i've been in this thread for 30 minutes now and that's not because i've been reading
and no i didn't, i was just watching over and over and over....