At this time there is no such version of the Cisco VPN Client that can work with servers. This is a design issue. Cisco VPN Clients are designed only for machines that can be clients such as Windows 98, XP, and 2000 workstations. Cisco VPN Clients are not designed for machines which are servers themselves because the functionality of VPN Clients conflicts with the architecture of the server machines.
Cisco VPN Clients are not supported for the Microsoft Windows family servers.
Note: You might damage the registry if you install a Cisco VPN Client on a server machine.