Ah, neither port forwarding or the DMZ will work reliably with a dynamic IP address.
My strategy for static config: get your DNS server numbers from winipcfg(98) [slect the lan adapter] or ipconfig (NT/XP) if the router passes them directly to the client through DHCP, if the router acts as DNS proxy then get the DNS server addresses from the router WAN connection info. Set tcp/ip on the client machine to static config, enter a private IP address outside the DHCP range of your router on the same netmask, enter the router IP LAN address as the gateway and enter your DNS server IP addresses. Presto, static config.
Got the DI-704P "quick start guide", gonna look at it now...