DynDNS Updater Instructions & Configuration
DynDNS Updater is a Windows dynamic IP update client: http://www.dyndns.com/support/clients/windows.html
Other services beyond DynDNS are supported with different configuration files. A DNS-O-Matic configuration file is downloadable here: Profile_dnsomatic.ini (text file)
Changes Needed to Config
For this client to support updating DNS-O-Matic, you must change your dyndns.ini file.
In default distribution, support for multiple DNS providers is disabled. To enable multiple providers support, create an entry IsDynDNS=0 inside [Options] section of dyndns.ini file.
If you do that, your dyndns.ini file will look like:
[Options] IsDynDNS=0
Value 0 enables multiple providers support, value 1 only displays support for DynDNS.org.
(Via Developer FAQ)