I recently configured Veeam to backup two VMs that were not on a domain. The servers are running Windows 2008 R2.
The behaviour of Windows Administrative shares has changed in Windows 2008 R2 and Windows 2012. UAC stops remote accessibility of these shares.
The following registry key will have to be added:
0 – build filtered token (Remote UAC enabled)
1 – build elevated token (Remote UAC disabled)
By setting the DWORD entry to 1, you will be able to access the administrative shares since the remote logon token will not be filtered.
See KB947232 for more information.