A:
The My Passport Ultra is compatible with Mac OS X Leopard, Snow Leopard, Lion and Mountain Lion. However, the drive is formatted as a single NTFS partition for compatibility with all updated Windows operating systems. If you want to use the drive with a Mac computer, you must reformat the drive to HFS+ format. Please refer to the link below for instructions on how to format the drive.
How to partition and format a WD drive on Windows (8, 7, Vista, XP) and Mac OSX
http://wdc.custhelp.com/app/answers/detail/a_id/3865/"