I finally talked my grandpa into making the switch to Apple. He just went out and bought a brand new 24" iMac. My grandpa has an external hard drive he used with his windows machine. He has all of his documents stored on the external drive. When I plugged in the external drive, the iMac didn't recognize it? Did it not recognize it because it is in a different file format? How can I get the iMac to recognize the drive? thanks.