I have just tried to change the registraton details of my free Zone Alarm as I needed to change the email adresss. It now says the registraton is 'pending' and I am nervous that a) Zone Alarm may no longer my working properly and b) I will not be alerted to any new updates which are available.
You probably shouldnt really bother registering. I skip it myself and once a month check for an update. The updates to a firewall are pretty well unimportant in comparison to sypware and AV protection. If a new version is present do upgrade but being 6months out of date will only put you at a fraction of a percent more than updating it.