How do I enable or disable "Network security: Minimum session security for NTLM SSP based (including secure RPC) clients and serve" in windows 7

An external lync user not able to connect to server.
On FrontEnd Server i got an error in event viewer telling: User authentication with NTLM protocol failed with error SEC_E_UNSUPPORTED_FUNCTION. This indicates a potential mismatch between security policy settings on the client and server computers.

Cause: This error can occur if the settings in "Network security: Minimum session security for NTLM SSP based (including secure RPC) clients" policy on the client computer are not the same as the settings in the "Network security: Minimum session security for NTLM SSP based (including secure RPC) servers" policy on this server.  By default, the "Require 128-bit encryption" setting is disabled for computers running Windows Server 2008, Windows Vista, Windows Server 2003, Windows 2000 Server, or Windows XP. For computers running Windows 7 or Windows Server 2008 R2, this setting enabled by default.
Resolution:
Ensure that the "Network security: Minimum session security for NTLM SSP based (including secure RPC) clients" policy settings on the computers from which users log on are the same as "Network security: Minimum session security for NTLM SSP based (including secure RPC) servers" policy settings on this server.
So i need to change the "Network security: Minimum session security for NTLM SSP based (including secure RPC) clients and serve" on the user machine wich is windows 7