Got a Western Digital My Passport Essential 320 GB HD for Christmas. Would like to use it. Box says formatted NTFS for Windows XP, Vista and 7. Requires reformatting for Mac OS X Tiger, Leopard or Snow Leopard. I have Mac OS 10.4.11. How do I make it so that I can use this Hard Drive. Only plan to use it for back up and additional storage. I don't know anything about using external Hard Drives. Please, oh please, help!