Thanks lesterb for the reply, useful info on backing up. So someone has done it...
So I've checked Win10x86, fresh from MS and stock setup doesn't work in supporting change of the pathnames, backing up to local disk. IE-11. Win build 14393.
I tried a few other changes, but the one that worked was:
Go to IE11, Internet Options, Security Tab, uncheck
restart IE11.
Ignore security warning, login to your Mini-NVR. I could change pathnames and also successfully perform a backup.
I repeated this on Win10x64, just unchecking the , and viola it also is successful. IE build 11.187.14393.0
There maybe other approaches that also work, but IE with Protected Mode disabled works for me in both x86 & x64 windows 10. I'd recommend re-enabling Protected Mode once you've done your backups.