Windows 2000 DNS

We have two domains, old.com and new.com. Old.com is and NT 4.0 domain and new.com is a Windows 2000 domain. We setup a DNS server in new.com to forward requests to old.com, but it is not forwarding requests properly. Is there any other settings that we are missing in order to get the two servers talking properly? We are currently using forwarders and root hints.

Old.com is using a 192.168.x.x network and new.com is using a 10.9.x.x network. Do the two domains need to be trusting each other?