WD My book Essentials works on my PC but won't let my Mac make any changes to it

WD External Drives External Drives for PC
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This is a Windows/Mac issue. A drive formatted NTFS for Windows is read only on a Mac. A drive formatted on a Mac is not readable on Windows. I’m not a Mac user but see if this helps http://www.cnet.com/news/how-to-manually-enable-ntfs-read-and-write-in-os-x/ Joe