DSL + DHCP

OK.
This sounds like some kind of security idea. I'm not convinced it is possible to do it like that, unless you have set up a
domain, and require domain logon on the workstations. Without a domain logon system, I think that the routing service
on the server will be available to all workstations, even without a logon to the server. To me this sounds unnecessarily
complicated for a small network setup... All users are supposed to be allowed to logon, I assume, and so they get
internet access. What is the difference, then, if they can go on the internet without logging in? Or are there unauthorized
persons on the premises?

In short, I think you need to set up a domain for this system. I'm sorry, but that is beyond my expertise.

Regards
/RID

Hmm sounds as though you requier the setup as per we have here,

All computers require logon from a valid account which is stored on the 2k server.

Everyone has to be authorised through this server before the can use any of the computers.

All users with accounts can log on to any machine with thier own desktop due to authorisation

Once logged on they can access the internet directly through our firewall which uses a squid authentication ( you can make the server do this if you need to regulate where people are allowed to go)

Router / Firewall has is own ip
each machine  has its own ip
each printer has its own ip
and the server has its own ip

DHCP is used from the server for laptops / mobiles pluggin into our network.

They also need to authorise through either thier own account or a guest account

Every user needs a username and password to access the internet.
Firewall software can regulate where and when they are allowed to browse.

If you do set this up in a small business you will need to write and issue an IAUP (Internet acceptable user policy) just to ensure they dont try to take you to court for something they seen opened ect ect.

Is this what you need?

If so I hope you have a lot of time as these things are not setup quickly.

Accounts, Privledges, Files shares, mapped drives, ips, dhcp range, routing, gateway etc etc all need to be figured out before you start.

First off, the DHCP is a trivial issue.  If you want to run it on the server and not the router (or vice-versa), turn it off in one and on in the other.  I think that router based DHCP servers are a lot easier to maintain and configure than Microsoft's, but it does put it at the firewall instead of behind it.  Either way, location will have no impact on its performance.

Now the meat, why do you need to have the PC's go "through the server" to get to the internet?  A network topology of

(A) ISP ---- router ---- server ---- hub/switch --+-- desktops
                                                  +-- laptops

doesn't really make much sense since you have to dual-home (install two network cards) in the server, you have to turn IP forwarding on (which essentially turs it into a router as well).  Also, it adds a point of failure - if the server goes down, has network problems, NIC failure, etc., then you've lost all internet access.  With a more normal topology

                                      +-- server
(B) ISP ---- router ---- hub/switch --+-- desktops
                                      +-- laptops

you don't have that vulnerability.  Configuration (A) does work if you intend to use the server as a screening router/packet filter/firewall, but 1) why do that if you already have a router in place and 2) if you are going to have a machine acting in that capacity, you certainly would not want it to be a server of any kind, especially not the domain controller - security wise, that's just way too dangerous.  The only that seems to make any sense is you want to do internet sharing through the server, but, again, that's something the router will be doing.

So, unless I'm missing something that hasn't been included in this thread, I'd proceed as follows using configuration (B)....

1) install router/firewall
 - turn off DHCP
 - assign public IP (either static of DHCP) to the "outside" interface of router/firewall
 - set ISP's DNS addresses (if required)
 - assign private IP (192.168.1.1) to "inside" interface of router/firewall
 - configure (harden) router/firewall with access rules, security, etc.
2) install hub/switch
3) build server
 - install Windows 2000 Server
 - decide if you want to run as an AD Domain Controller or just a member server
     for this, unless you require a domain structure, just install a member server
 - configure a static IP (192.168.1.2), set gateway to 192.168.1.1
 - install DHCP server
 - specify DHCP pool (192.169.1.16 to 192.168.1.254)
 - specify default gateway to pass along to clients (192.168.1.1)
 - specify DNS server addresses to pass along to clients (from ISP)
 - if installing as a domain controller, set up user accounts
 - might want to setup a WINS server here too, just a suggestion
4) build workstations
 - join appropriate domain or workgroup
 - set TCP/IP properties to get DHCP address

If there is a specific reason for using configuration (A), please let us know.

Get a good network plus book.  I passed mine with flying colors.  The responses here are much too elaborate and drawn out.
If you want to expose this server to the internet for such things as a mail server or webserver, it should either be placed in the DMZ of the router, or moved to the direct connection and the router could be eliminated entirely.  If yuo have already bought the router and are pressed for cash, I can tell you really quick how to turn a router into a really expensive ethernet switch.