Since your Core is running on an Innous Zen MkIII, then you will first need to share a folder on your desktop PC over the network. Then you can add that folder share as a network connection to your Core.
The backup is made from the machine running the Core (in your case the Zen MkIII). You are using the desktop PC to run the Roon user interface to control the Core.
You need to first add it. Being a Windows share, you’ll also need to use the Username and Password for the Share that you have created…
Edit: oh and another wrinkle that Windows 10 has added is that if you’re using a Microsoft account that is tied to an email address, you don’t use the email address as the username, but need to use the underlying Windows local account username…
So, for example, my local account username is the folder name of my root user folder. I.e. my root user folder is C:\Users\gcoup , so the username I type in to the Add Network Share setting screen of Roon is gcoup, and then my password into the Password field…
Ah, no, I don’t use a Workgroup - at one time all my computers were in a Homegroup, that is, until Microsoft decided that the Homegroup feature was more trouble than it was worth and killed the feature. It still pops up now and then in menus, like Banquo’s ghost…
Shot in the dark - I know that Windows generally isn’t case-sensitive, but try “Peter W B Coles” instead of “peter w b coles”?
Failing that, perhaps you can use the Security tab on the Windows Share Properties to add an explicit “Roon” user…? I’ve done that before now for third-party software that needed access to a shared folder…
Have you made sure to actually share the folder before adding into Roon? I would do the following:
1 Open the Peter W Coles folder
2 Create a new sub-folder there called Roon Backups
3 Right-click the Roon Backups folder that you created and open properties
4 Go to the Sharing Tab
5 Press Share
6 Note the username that appears there, this is the one you will have to enter into Roon
7 Press Ok to share the folder
8 Note the Network path specified in the sharing window and enter this into Roon
9 If it does not work, please provide screenshots of steps 6 & 8