If you're running DHCP on a Windows 2003 domain controller that is also running DNS, you may see Event 1056 (see link) errors in the System log.  This is because DHCP does not have separate credentials (a domain-user 'service' acct is recommended) for DNS dynamic registration.  The danger here is that DNS records could be overwritten.  This is not a default config, but Microsoft recommends you use separate 'DNScredentials' or not run DNS and DHCP on the same domain controller. [more] See the link below to enter the credentials into the DHCP mgmt console.