Okay, let's try this to put it all together.
1. You will need a cable/DSL router to pull this off. There are several on the market that will work. Most will also act as a firewall.
2. Your physical connection will essentially look like this: cable modem <--> cable/DSL router <--> hub <--> computers.
3. Your configuration will essentially be as follows:
On the router, set the WAN side (from ISP) to accept DHCP info from the ISP. Make note of ISP's DNS server(s) IP address. On the LANside (your internal network), do not set the router to act as a DHCP server. Your router will also act as the gateway for your local network.
I'm assuming you are using Active Directory. AD must have access to a DNS server which allows dynamic updates (most ISP DNS servers do not). Therefore you will need to set up a local DNS server to service your private network. Also since you want to use DHCP (which requires a fixed IP address), I would setup both DHCP and DNS on your Win2K server. Make sure you assign IP addresses in the private IP range for your DHCP scope. Give your Win2k server a fixed IP address in this range and have the server point to itself for the primary DNS. Also set up DHCP to point to your local DNS server. Once you have DNS set up, set it to forward to the ISP's DNS server.
What all this in effect causes to happen is the following: when a client submits a DNS query, it will go to your local DNS server first. If the query can be answered by the local DNS (queries involving all your local resources), nothing will go to the ISP's DNS server for resolution. If the query can't be answered locally (all queries involving the Internet), it will be forwarded to the ISP's DNS server for resolution.