Per the above posters, no matter what Windows format it is using, FAT32 or NTFS, it will be readable by the new Mac. So, your friend can just plug the drive in, and it should show up on the desktop. Then, to convert it to the native Mac format (recommended unless he/she wants to use it to share files back and forth with Windows) just open Disk Utility and use it to reformat. Disk Utility is found in the Utilities folder on the Mac.