Hyper-V introduces the concept of virtual machine snapshots - which is to say point in time images of a virtual machine that you can return to at any stage. These snapshots are implemented in the virtualization layer - and can be taken at any time with any guest operating system (even during an operating system installation). Snapshots can be taken whether the virtual machine is running or stopped. If the virtual machine is running when the snapshot is taken there is no downtime involved to create the snapshot.

Snapshots can be created in the Hyper-V Manager (by selecting a virtual machine and selecting Snapshot from the Action menu or panel) and in the Virtual Machine Connection window (by clicking on the snapshot button in the toolbar or by opening the Action menu and selecting Snapshot...).

Selecting to create a snapshot from the Virtual Machine Connection window will result in a dialog that allows you to enter a custom name for the snapshot (e.g. "Installed Office 2007" or "Just before I do something stupid and ruin the virtual machine"). If you want you can dismiss this dialog and have the snapshot use an auto-generated name. This auto-generated name will consist of the name of the virtual machine followed by the date and time when the snapshot was taken.