If you want a drive to backup your Mac, you can get another WD hard disk and reformat it via the Disk utility on the Mac and it will be totally usable "on the Mac only". On the Mac, go to the App Store and download/install OneDrive for Mac and transfer your files in that fashion. Since you already have the hard disk formatted for your Windows system, keep it that way. On a Mac but you cannot write to it (it will tell you it is locked). A hard disk formatted from a Windows computer can be read To all of you Apple uses a customized NTFS file system which does not exist in the drive table recognized by Windows and there is no patch or fix unless WD may have an app that can be installed.