A client to update the IP automatic with http://freedns.afraid.org/ It is a Windows Service that works in the lastest versions of Windows (Windows 7 and Windows 2008). Also it has the possibility of sending an e-mail whenever the IP changes.
DotDNS is a Dynamic DNS client and server software that can work with your own domains. It will work on standard W2K/W2003 servers. *UPDATE* MSSQL Express is designated as backend for storage.