make sure your firewall has inbound and outbound ports for PPTP and gre open
need to add dhcp or server assigned ip address pool for the vpn clients
bad choice for internal server ip to be on 192.168.1.0 network as most home networks have this ip range, and your default route to the vpn server will be this ip
change it to something 192.168.100.2
make sure your default RRAS policy is enabled, as well as enabling user account for dialup remote access
give this server external ip address and in your firewall statically nat it to the public ip i.e 192.168.100.2/24 will map to 151.216.150.206
presuming this box sits behind a firewall, it will work with one nic card
If this box is going straight to internet router (not the best setup) then dual nic scenario - one public interface with internet router as gateway, the other to internal lan
here is link from microsoft for reference for basic setup:
http://support.microsoft.com/kb/323381
