basically
Start - programs - administrative tools - routing and remote acess
start the whole thing
start the wizard...
(x) choose NAT protocol...
answer the question (about your connection)
(x) route ip packets on this interface
also
you have to enable DHCP on the server
and configure the clients to get ips dinamically ... configure the IP of the server as the DEFAULT GATEWAY on all clients...or even better...configure the DHCP to tell the clients their DNSs (your ISP dns server ip or your dns server ip if it is a intranet) and the default gateways(Your ISP ip, routing from internet...or your server ip ,routing on a Intranet) and leave the clients settings alone
that should work
have fun...
