Windows Pro 2000 acces to network

I am upgrading a existing WIN NT 4.0 network to WIN 2000 Server and 2000 Pro workstations.
My question is this, the existing local domain name, domain1 is not recognized by the WIN 2000 Pro. It only recognizes the proper domain1.com name. Is there any way to use the existing domain1 simple name model with the 2000 network. THanks in advance