A:Answer No. If you want to reformat it for OSX, you can do so with the Disk Tool. if you want it to be able to read and write to it with a Windows computer also, format it to FAT32, an old Windows format. You can also buy 3rd party software so you can use the modern Windows NTFS format and read and write to it with a Mac or Windows.
If you are just using it on Mac, format it for OSX.
