See Knowledge Base article Q246804.
Here are excerpts from the beginning of the article:
"Windows 2000 supports dynamic Domain Name System (DNS) updates (per RFC 2136). This behavior is enabled by default for Windows 2000 DNS clients.
Depending on the configuration and services running on a particular computer, different components perform dynamic DNS updates. There is no centralized way (such as a tool or registry keys) to manage the dynamic DNS update behavior of all components. This article describes each component and how to modify that particular component's behavior."
"The following components perform dynamic DNS updates:
DHCP Client service (all Windows 2000-based computers).
DNS Server service (Windows 2000-based DNS servers only).
Netlogon service (Windows 2000-based domain controllers only).
RAS client (Windows 2000-based RAS clients only).
Dynamic Host Configuration Protocol (DHCP) Server service (Windows 2000-based DHCP servers only)."