I had a external HDD be4 but i returned it due to the fact that it was usb external HDD. It was a 1 touch back up device but said it's uncompatible unless you have firewire hdd. Which I did not have because it was the USB model from Western Digital. But does it really matter if it's USB or IEEE 1394a? Can you still use a usb hdd to back up your OSX and media files? Only reason I wanted to get one because my music was taking up my entire Mac HD. So after that I became confused in which external HDD i should get or even use for my powerbook.