By default, the DHCP server service runs in the context of the domain controller's computer account, and has full control of all DNS objects, allowing older DHCP clients to overwrite dynamically registered DNS records.
I recommend that you configure an ordinary, non-restricted, user account, with a non-expiring password, and use it in DNS Credentials, specially when the DHCP and DNS server services are running on the same domain controller.
Use either of the following to configure DNS Credentials.
DHCP Server snap-in:1. Open the DHCP Server snap-in from Administrative Tools.
2. Right-click a DHCP Server that you want to configure and press Properties.
3. Select the Advanced tab.
4. Press the Credentials button.
5. Type the UserName, FQDN (Fully Qualified Domain Name), and password of the account that will run the DHCP Server service.
6. Press OK and OK.
Windows Server 2003 Netsh:Open a CMD prompt and type:
netsh dhcp server DHCP_Server_IP_Address set dnscredentials UserName FQDN Password