If you want to make a clone / copy of an existing Windows 8 Hyper-V client virtual machine, follow the steps below:
Run Import wizard
Run the Hyper-V manager.
Click [Export Virtual Machine…].
Choose a export folder eg [C:\VHD\W8RLIDEV2012]
I will always move the contents of the created folder to the root folder, see screendump, but this is not necessary.
Click [Import Virtual Machine…].
On the Locate Folder page, enter the folder containing the Virtual Machine you want to clone / copy eg [C:\VHD\W8RLIDEV2012\Virtual Machines]
On the [Choose Import Type] page choose [Copy the virtual machine (create a new unique ID)].
I use the location of the virtual machine to store snapshots etc.
On the [Choose Folders to Store Virtual Hard Disks] choose [C:\VHD\W8RLIDEV2012\Virtual Hard Disks]
The last thing I do is rename the Virtual Machine in the Hyper-V Manager.