How to backup to a "System Folder"?

I have “GMailFS” installed… - GMail Drive shell extension
It turns your Google Mail account into a filesystem. Its implemented as a "System Folder. I see it under Control Panel on “My Computer”. There is no drive letter associated with it. It works fine for copying files to/from folders, and I’ve created a few subfolders on it.

Anyway, I’m playing with comodo backup, and when I create a new backup, and go to Destination, and Browse, I see “Gmail Drive” listed in the tree. But, when I click on it, the OK button greys out. If I click on some other folder on the “Browse for Folders” window, the “OK” button comes back. Why won’t comodo backup let me select this filesystem/folder?

While this is an old topic, i wonder how is it get listed by running the following command from command prompt:
net use