I'll try to make this short, but still detailed.

I have a small office. 5 PC network through an HP Procurve switch to a
Windows 2000 server. The server hands out the IP addresses.

Originally set up Ameritech DSL. Of course the Efficient 5861 DSL
modem/router also wanted to pass out IP addresses. It was easy enough to get
tweak it and us NAT to make all the equipment happy. Every system in the
office could both go online and see the server and the rest of the network.

Now, AT&T Yahoo took over. Without bothering to mention it to anyone, the
first thing they did was to get rid of our DSL line and move our DSL over to
our fax line (I have about a dozen phone lines coming into the office). Of
course, we figured it out when we couldn't get online or send/receive

Moving along, here's where I'm at now and my problem.

The 5861 died right about the time all this was happening. It got replaced
with an "AT&T Yahoo! Speedstream 4100".

Now I'm back to the 4100 and the server both wanting to assign IP addresses.
The 4100 is nowhere near as tweakable, so I'm rather lost on how to deal
with this. I can make it so you can get online OR connect with the server,
but not both.

I'm thinking I can just put a router between the Procurve and the 4100 and
solve this. Is that correct? If so, any ideas on exactly how I'd want to set
that up (settings)?