DO NOT BUY WD MY BOOK DRIVES if you plan to store anything of value. I and a friend started buying My Books to build music and video libraries to work with iTunes and AppleTV. He has had all 4 of his drives fail and I’ve had 4 of five fail. I work in the software industry and deal with a large amount of hardware and the WD My Book has the highest failure rate of any drive I’ve ever used or seen. In my personal use, it is the only drive I’ve ever had fail. Costco used to sell them but no longer carries them because of the high failure rate and returns that they had to deal with.
The only WD external drives I own that haven’t failed are the Passports. They seem to work endlessly. Just avoid the My Books.