One of the advantages of virtualization is that it lets you test applications (and in some cases, hardware devices) in an isolated environment. But once you soil that environment with software or drivers, it’s no longer the “clean room” it once was. Rather than delete the virtual machine and start over, there are ways to revert back to earlier stages—an undo, if you will—to save you time and trouble.
If you’re using VMware Workstation, just open the VM menu, select Snapshot and then Take Snapshot. Name the snapshot and click OK to save the current state to your hard disk. Thereafter, changes you make to your virtual hard disk (software you install, files you delete, etc.) are saved in a separate file on your real hard disk.
You can revert to a saved state at any time; from the VM menu, select Snapshot→ Snapshot Manager, select the snapshot you wish to use and click Go To.
Microsoft Virtual PC doesn’t have a snapshot feature, but you can get a crude approximation, provided you have enough free disk space. When the virtual machine is in a state you’d like to save—like right after you’ve installed Windows and VMA—shut down the virtual session. Then, open Windows Explorer on the host and navigate to the folder containing your .vhd virtual hard disk (usually Documents\My Virtual Machines). Using the right mouse button, drag your .vhd file to another part of the same folder and select Copy Here, creating a duplicate copy (e.g., Windows 7 - copy.vhd); that’s your snapshot.
To revert to a saved state, make sure your Virtual PC session is shut down, and then reopen Windows Explorer on the host. Delete or rename the .vhd file in use, and then rename the backup (e.g., Windows 7 - copy.vhd to Windows 7.vhd).
