Rename default value in username "Unregistered"

[sisterj]

Hi, I'd like to remain the default value in username from "Unregisterd" to something else. I don't want to change the username group or the title "Guest" just the default value so in case someone doesn't write in their name, it doesn't default to "Unregistered" but rather another label such as "Visitor". I tried various solutions including changing the class_bootstrap.php file -- from $vbphrase['unregistered']; to $vbphrase['visitor']; but that didn't work. (I'm a definite novice at this stuff but willing to try stuff). I'd appreciate your help.