Just upgraded my late 2007 MacBook Pro Boot Camp partition to Win 8 RTM and was in the process of re-installing several apps. The Cisco VPN Client we use to connect to our corporate network was a bit finicky. There are a few workarounds to get it running on Win8.
First, you need to fix the following registry key to resolve error 442 Unable to enable virtual adapter:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CVirtA\DisplayName
It will be set to something like “@oem8.inf,%CVirtA_Desc%;Cisco Systems VPN Adapter for 64-bit Windows” – drop everything before “Cisco Systems” from that value.