Freddy, glad you got your issue resolved! It's just too bad it's not that simple for me 8)
 
I'm unfamiliar with what IP forwarding is exactly. I'm also unclear whether we should have a default gateway or not. Basically, it's a small office, with one main server (WAS connected to the internet, but now it's a seperate machine) running DNS, DHCP, AD, etc. So any internet (external) requests just get routed through the ISA server machine.
 
:edit: Oh yeah, the main server is also running stuff like Exchange 2000, SQL Server 7, Borland Interbase, ISA Server is still installed, but the services are stopped.

0.0.0.0 is a legitamate IP address in the sense that it is actually a broadcast sent by a DHCP client as part of thr DHCP Discover. as follows.
The first time a DHCP client computer attempts to log on to the network, it requests IP address information from a DHCP server by broadcasting a DHCPDiscover packet. The source IP address in the packet is 0.0.0.0 because the client does not yet have an IP address. The message is either 342 or 576 bytes long—older versions of Windows use a longer message frame.
 
In other words, your machine is trying to obtain an IP address.
 
In regards to switching between Native and Mixed Mode for your environment, I see no compeling reason ATM.
 
ISA server is running on the DC? If so and if its multihomed, then the inside nic should have NO default gateway. If the modem is configured as a dial out, then the inside nic still doesnt need a gateway.
 
This is where I get lost in this thread .... Your DC/ISA server does its own DNS? Does it use root hints or forwarders? Forwarders would probably be more efficient in the scenario.
 
Have you tried another NIC? I have encountered that malfunctioning NICs can cause only a partial DHCP process .... only doing some of the 4 required steps to get a lease.
 
169.254 for an internal network should only be used for diagnostic testing and not necessarily the IP standard for your network. Just my opinion for that.
 
If there is anything that I didnt explain clearly or I am missing something, feel free to ask.

My apologies for the long delay. I found the problem that we were having here. It was the Firewall Client installed from the ISA server. I don't yet know what was causing the lack of connectivity, but removing the Firewall Client allows the system to boot totally normal afterwards. But thanks to everyone who took the time to troubleshoot. Much appreciated.

Folks
 
I have the same problem (static ip works, dynamic ip doesn't) under XP.
 
It's not the Norton problem - I did work through that solution.
 
How do I find the DHCP startup log?
 
Thanks - Vince Melling

Go to "Services" and enable "DHCP client."

Here is the solution (it worked with me!!).
You must download this utility, called WinsockXPFix, and execute it, so that it fixes your TCP/IP problem.
Download it from here:
http://tntmax.com/Download/Software/WinsockXPFix.exe
 
Best wishes!!
MasterU

That is a neat piece of software, masteru. What I found intriguing was how many people had this problem from running Ad-aware.