Is this possible to make that user can connect before logon to windows?
One reason - sometimes for remote admin is nessessary to logon as administrator, but then is no connection.
You want to use "logoff on connect". Read "Logging into Windows through a Secure Tunnel" on p. 671 of the 7.0 Admin Guide.
It is possible to start the Network Connect session during boot time using GINA (XP) or Credential Provider (Vista ,Win7).
There is no option to have userA logout and log in as userB with a valid session; the session will be terminated if done.