computer with two nics

I am using a Mn500 router and have succussfully setup
four computers on it using the default 192.168.2 network
using XP, ME, 98 and 2000. I am studying for computer
certifications and on one of these computers i have
installed another nic and gave it an address of
192.168.100.1. This computer is running 2000 server and
i have set up RRAS to become a router. I attached
another 2000 server machine through a crossover and
assigned it 192.168.100.1. This machine is able to get
through to the internet. It can also access shared files
on the 192.168.2 netowrk only by using IP addresses but
not FQDN's. Computers on the 192.168.2 network cannot
access this machine at all. I can ping both NIC's on the
machine with two nics but nothing beyond that. I played
around with the IP routing table but to no avail. Any
IDEAS? Any help would be appreciated/