At the moment we share internet access on Windows NT 4.0 using SBS
4.5? I am not sure how we share it any info would be helpful?

I know its NAT that is doing the sharing (I think) but how is it

We also have DHCP running.

I changed the Server TCP/IP settings to include a default gateway.
I also added this to the DHCP settings to include a Router (gateway).

I want to have a router/firewall in place but have tried to set it up.
However the Server could access the internet (it has a static ip
address) but the clients could not.

When accessing the internet they were getting the logon screen for the
router?? They had the default gateway as the router ip address.

I am not sure what to do, any help would be appreciated.