Access to C:\ over HTTPS?

Could I use this to share my entire C: drive, e.g., over HTTPS, or is this restricted to a folder under wwwroot?

No, there is no restriction, you can share any folder on the server. However the folder should be accessible by the Windows identity that is used to run the application.

As a related question - I host several web-sites for clients and would like to allow each of them to manage their own files.

Can I set up multiple virtual roots and give each user access only to their own root?

I tried installing FV more than once and that didn't go well!  

As a related question, is the path for root folders a local absolute?  ie; is C:\SomeFolder a valid entry?  

Yes, you can set up multiple root folders and assign them to each user.

The path for root folders can be physical or virtual. So c:\somefolder and /somefolder/ are valid entries.

In your case, you may create root folders like c:\AllUsers\user1 and c:\AllUsers\user2.

Can it be on another server?

Like use \\servername\folder_location ?

Exactly my question! 
I  have several servers that are mapped to drive letters when the user logs in - so I need to access those volumes as well.

I was expecting either the drive letter to work or at least \\server\share to work but neither seems to work.

Hopefully there is some solution - as this looks like a great product so far!

PS: I am the sysadmin for Syracuse Invitational - just so you folks know I am now a registered user and not just using the trial!

In theory it should work fine using a mapped drive, like \\server\share - e:\share (e being the mapped drive).

I havent tested this myself, but I can and see if I get any kind of wierd error.  I will let you know.