Cisco VPN has been a standard my company has used for quite some time. Although there are other VPN tools out there that you can finesse to work with Cisco client profiles and protocols, this article relates to continuing to use Cisco VPN Client 5.x.
Almost every install I have done has yielded an adapter error. It turns out this is caused by nothing more than a description in the registry for the VPN adapter. Not a driver issue, not an NDIS issue, not a TCP stack issue.
The key that is the culprit is:
The value for this key will list an oem file a comma, a text description, and thus is where the problem lies. Simply edit this key, and remove everything but the text description of Cisco Systems VPN Adapter. Close the registry editor and walla, you are done!