Can you reach the vmware-based 2003 domain controller by ip-adress/FQDN? In other words, is your 2000-server able to reach your domaincontroller?
As I see it, there is two scenarioes you could follow for troubleshooting this one:
1) Make sure your 2003 domain controller is operational and is connected to your network
2) Make sure your servers/clients can reach this domaincontroller (they need to be configured with a DNS-server that contains the service-records for your domain.