Here is how I set this up last night. I use DHCP on my LAN, but that isnt a requirement for you.
1. Install 2 Nics on the server (preferably 2 DIFFERENT brands, it will make IDing them easier)
2. Install Client for MSN, TCPIP, And File/Printer Sharing on both NICS
3. Unbind File and Print sharing on the Card you are going to plug your cable modem into (this is the WAN and u dont want FPS on that)
4. go to TCPIP...advanced...WINS...and enble netios over TCP (ONLY DO THIS FOR THE LAN CARD...not the WAN card)
Now decide if u want DHCP on the LAN or not...lets assume you dont. Assign 192.168.0.1 as the IP for the internal nic and a 255.255.255.0 for the sub. You will also need the DNS addy of your ISP and enter that there. The WAN card leave alone, since it will be assigned an IP through DHCP from your ISP
On your clinets confige the nic cards the same way you did the internal (LAN) card on hte server.
For IP use 192.168.0.2 and so on. For gateway you want 192.168.0.1
Now, on the server install Routing and Remote Access.
Go to the RRAS manager. Right click on Server Status and click add server.
It will ask which one..choose "this computer"
Wait for the server to be added...then right click on the server name and choose "configure and enable RRAS"
A wizard will pop up and ask you some questions.
I am not at my machine right now..so things are a bit fuzzy..bear with me.
It will ask what type of server u want..say internet connection sharing
Then it will ask if you want ISC or NAT based...choose NAT
Make sure that the RRAS service is started and set for auto start.
Thats all there is to it. I wish I was at the mchine so I could make sure that I did all that in order, but it should be enough to get you on the right track