if you only want 120gb buy a new internal, you can get huge internal drives for pennies. if you're going external, seagate, WD and Lacie are all good. portable drives will run off usb, desktop ones will have a power supply. you can get 500gb for less than £80 everywhere, and probably for about 60 online, but you're best off not looking at anything under 320gig because it wont be economically viable.