Enable VSS backups of VM’s running on Hyper-V using Windows Server Backup.

If you want to backup your Virtual Machines running on your Hyper-V server using the Windows Server Backup feature, you need to manually create the following registry key on your Hyper-V server: 

HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NT
CurrentVersionWindowsServerBackupApplication Support{66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE}

Name: Application Identifier
Type: REG_SZ
Value: Hyper-V

First, if you not already done so, add the Window Server Backup feature from the Server Manager because it is not installed by default. Create the key and the String Value. You can also download this file, rename the extension from .doc to .reg and run it on your Hyper-V server.

Source: Microsoft KB 958662

Cheers!

– Marek.Z