Your network contains a server named Server1 that runs Windows Server 2008 R2.
Server1 has the Hyper-V server role installed.
Server1 hosts a virtual machine (VM) named VM1.
You take a snapshot of VM1 at 05:00 and at 19:00.
You use Hyper-V Manager to delete the snapshot taken at 05:00.
You need to ensure that the files created by the 05:00 snapshot are deleted from the hard disk on Server1.
What should you do?

A.
At the command prompt, run the rmdir.exe command.

B.
From Windows PowerShell, run the Remove-Item cmdlet.

C.
From the Hyper-V Manager console, shut down VM1.

D.
From the Hyper-V Manager console, right-click VM1 and click Revert.

Explanation:
When you delete a snapshot, the .avhd files that store the snapshot data remain in the storage location until the virtual machine is shut down, turned off, or put into a saved state. As a result, when you delete a snapshot, you will need to put the production virtual machine into one of those states at some point to be able to complete the safe removal of the snapshot.
Source: http://technet.microsoft.com/en-us/library/dd560637.aspx