Issue mounting a NTFS USB drive

I have converted my Win PC to Zorin OS. the install went OK and no issues with recognizing any peripheral devices with the exception to my WD 1TB USB drive that has the backup of all my info and files.
The WD has three main sectors - one acts as CD-ROM and Zorin can see it, the second is the encrypted part that was used for backup and is driven by the application that is on the CD sector - Zorin cannot see that as well. The third is just a big sector to where i just copied my Windows USER folder - surprisingly Zorin refuses to mount it. I can see it only when I am going to "my computer" and then it identifies it as "unknown folder" and when I try to mount it it give me an error message saying it cannot be mounted by Zorin with no more info. How do I make it visible?

You have provided the answer in your post - encryption! This will only be seen by Windows if that is what you encrypted the folder with - one reason why I avoid encryption on any system - every time (In Windows) you do a reinstall, the machine name generated will be different and any files or folders encrypted with an earlier install will become unreadable - I hope you created an Image of your Windows installation! I am not sure about external drives but dual booting with Zorin on the same drive would be able to read and write to NTFS files - but not encrypted ones!

Thanks for the quick reply, but unfortunately this is not the case. As I mentioned in my question there are 3 sectors in the USB drive - 1. CD_ROM 2. Encrypted data 3. data that was just copied into the USB drive from the PC HD (w/o encryption). I can see the 1 sector, I can see the second sector (but not access the data as it is encrypted). I cannot mount the third sector and this is the one I am trying to get to.....

OK, before booting your machine up next time, make sure your external drive is NOT connected at boot time. Once booted into Zorin, see if attaching the drive after it has booted has made a difference. One last comment, if your drive was connected and Windows was not shut down properly (cleanly) before installing Zorin, this will make partitions inaccessible!