The WD Passport is an excellent choice for a portable drive, and it comes with a case, I have a 160GB one. But at the time of purchase, all that I had was a laptop. So I bought a Seagate Free Agent (500GB) backup drive that has a separate power supply. They do make similar drives with as much or as little capacity as you want. Originally, I was going to purchase a 320GB backup drive, but fellow members suggested that I get a 500GB, the extra cost was around $10, but the extra space is worth a lot more than that. WD is among the best of drives, whether internal or external, or backup drives. They have a wide variety to meet most any need.