Im going to pickup an external drive on the weekend and while not new to computers in any way, have only owned my MBP for 3 or 4 months. I made the assumption that an external drive is an external drive, and can be formatted in NTFS or whatever os x uses. But i noticed there was a mac version of the h/d, which cost an extra $40 or so. Is this crap (ie i cant be formatted to use any os), or do i really need to buy a mac specific h/d, as they are hard to get through normal pc shops and any local mac shops charge stupid amounts.