how to setup VPN

[fosiul]

Hi,
I have linux box working as a router for internal networking. This linux box is getting lnternet connection from a lynksys router.
in my internal network, i Have windows 2003 server, which is acting as active directory ,dns , dhcp for other computer.
IP at lynksys router is :192.168.1.10
Ip at linux box is :192.168.1.1
and 194.132.235.1

internal network
windows 2003 server is : 194.132.235.2

My question is :
how i will setup Vpn connection so that, user can access this network via windows 2003 server active directory and routing and remote access

Can any one give me solution ??
check the diaagram pls