Apparently you're out of luck. According to Wikipedia:
Although Shadow Copy service will remain intact, the ability to create
persistent shadow copies will be removed from the future versions of
Windows, codenamed Windows 8 and Windows Server 8. Consequently, the
Previous Versions feature which exposed this functionality will also
be removed. Shadow Copy service will only be able to create volatile
shadow copies for backup purposes. Microsoft says negative impact on
performance and low usage is the reasons behind the removal of this
feature. As for accessing older versions of the user file however,
Microsoft will add a new component called File History to the
aforementioned versions of Windows. This component will replace Backup
However, I'd see if there's a way to play with Volume Shadow Copy command-line options (VSSAdmin). I don't have Windows 8 at hand, but it's worth a look.
VssAdmin is used to create, delete, and list information about shadow copies.
It can also be used to resize the shadow copy storage area ("diff area").
VssAdmin includes commands such as the following:
create shadow: Creates a new shadow copy
delete shadows: Deletes shadow copies
list providers: Lists all registered VSS providers
list writers: Lists all subscribed VSS writers
resize shadowstorage: Changes the maximum size of the shadow copy
VssAdmin can only be used to administer shadow copies that are created
by the system software provider.
VssAdmin is available on Windows client and Windows Server operating