I want to make sure that I can stop a machine, on Hyper-v with windows VMs, and then I can start it, being sure that nothing changed inside the VHD.
Is this possible? Can I make like an MD5 of "C:\Windows\System32\config" SAM, System, etc, and then start the VM's (after one month or more) making sure that nothing changed?
Is there other way, a more "pretty" way?
Perhaps an export off all drives like: "DIR c:\*.* /s/one >c:\before.txt"
and then a "DIR c:\*.* /s/one >c:\after.txt" then a file compare?
Microsoft provides an MD5 utility, though it is unofficial. It's called "fciv" (File Checksum Integrety Verifier). It can output directly to console or to an XML file depending on what you're doing with it, and even has the ability to recursively dive into a directory if you want to check and entire hierarchy of VHDs.
Details here: http://support.microsoft.com/kb/841290
You could use immutable disks. Base and differencing disks in Hyper V.
http://technet.microsoft.com/en-us/library/adfs2-how-to-setup-lab-environment-for-federated-collaboration-01%28WS.10%29.aspx
http://www.ucgurus.com/create-a-virtual-machine-using-differencing-hard-disk-hyper-v/