Solved WD Passport only works on mac - need to copy all files (in GBs) to Windows solved WD HDD from iMac won't show up with Windows/Mac as external HDD. I downloaded NTFS-3G to be able to read and write to my Mac and Windows. So, I just bought a WD Passport Ultra 2TB to use for changing files between a Windows and a Mac.
If you have installed any WD software on your computer be sure to remove it completely.