After reinstalling Windows 10, backups to my external hard drive stopped working. Seems that software that came with the external hard drive did not support backup of documents in OneDrive folder on C Drive. Work around was to start using 2X Feature of Mozy software that enables users to schedule simultaneous backups to Mozy's cloud service and to external hard drives. Thanks to Mozy for adding 2X feature!
If you have updated Windows 10 to the latest version "Fall Creators Update" version 1607 or if have just installed the latest version of Windows 10 version 1607 then the functionality of One Drive has changed.