I would like to find out if it is possible to have dynamic updates between a Cisco Router's DHCP server and Windows Server 2003's DNS server.
Is it possible for Cisco DHCP Server to send these registrations to a DNS Server on a remote Windows Server?
No, it is not.
With a Windows DNS Server, the client "registers" by writing its address into the DNS file. With a Cisco DHCP, the client does not "register" anything. The DHCP server assigns an address to the client, and stores the information.
You would need to have a process that reads the router config, obtains the DHCP information and then writes it to the DNS Server. The router itself has no mechanism to do this.
No-one has commented on this in the intervening months. For the benefit of Google Groups and others: A Cisco IOS DHCP server is quite capable of sending Dynamic DNS Updates to a DNS server. The version 12.3 and later documentation includes a guide to Dynamic DNS Support
that has step-by-step guides.