Well, if you still want a particular user to have a new name without having to reregister and still keep all their old messages intact with no "unregistered" as their name, do the following.
Open up ubb_library2.pl
Find:
After that, add:
All you're doing is fooling those reading the messages and UBB into thinking it's a new person. They will still have to log into your forum with their old name, but any posts they make will be posted using the "New_Name_of_User" that you define.
peetwokewl4u!