This will shutdown your virtual machines, copy the .vhd virtual hard disk files (not snapshots) to a backup location, and then power your virtual machines back on.

Install the Windows PowerShell Feature

1. You may need to install Windows PowerShell on your Hyper-V host machine, Server Manager -> Add Features.

Learn Some PowerShell Basics

1. A PowerShell script is a plain text file with the extension .ps1.
2. To execute a PowerShell script, open Run and enter:
   powershell.exe c:\myscript.ps1
3. The -noexit paramater will keep the command prompt open after the script has finished executing:
   powershell.exe -noexit c:\myscript.ps1
   * don't use -noexit if you're calling a script from a batch file, execution will stop at the end of the script and never return back to the batch file.

Set PowerShell Execution Policy to Allow Unsigned Local Scripts

1. If you run a PowerShell script for the first time, you'll probably encounter this error:
   File C:\scripts\test.ps1 cannot be loaded because the execution of scripts is disabled on this system. Please see "get-
   help about_signing" for more details.
2. You can read the details here, or just execute the following command within PowerShell to allow your own scripts to run:
   Set-ExecutionPolicy RemoteSigned

Download the Backup Scripts, Customize, and Schedule

1. Download the files here.
2. If you unzip the files to c:\scripts\vmbackup, then most of the paths will be correct.
3. It's just been brought to my attention that you need to Right-click VmBackup.bat -> Properties -> Unblock, or you'll receive an error about the script not being digitally signed.  Thanks Almoonir!
   
4. Modify VmNamesStop.txt with the names of your virtual machines, your domain controller should be last.
5. Modify VmNamesStart.txt with the names of your virtual machines, your domain controller should be first.
6. Modify VmBackup.bat to copy your vhd files to your backup location.
7. Create a scheduled task to run VmBackup.bat regularly.

Notes (UPDATED 9/25/2008)

1. I used a PowerShell script written by the InfoTechGuyz, nice work!
2. I ran a full backup last night and I made the classic mistake in forgetting to turn my domain controller off last, and then power it on first.  To accomplish this, I created 2 lists of VMNames.txt, one for stopping the VMs (DC last) and the other for starting them (DC first).
3. Snagged the cool powershell image from Tore Lervik, who created some handy powershell scripts for HyperV.