Question : Restrict access to network

We have a outside user thats not an employee of the company that will have access to one server on the network. he uses rdp to connect to my public ip then is redirected through the pix to the private ip the act server. since he is not an employee he is not in active directory. he needs to connect to the server its a real estate database. I could have him use the microsoft vpn to connect to the lan then access the server
I need him to connect to the server but how can I restrict him from accessing any other computer, share on the network. Can I use group policy to restrict that PC from accessing other resources on the lan, so he can not install software, access shares;
How can I accomphlish this?

Answer : Restrict access to network

As long as he doesn't know any domain username/password => YES

He will only be limited to that machine with user privileges.

Cheers,
Rajesh