Sorry, but in this message board system, you (or I) cannot change your user name. And you cannot create a new account using the same email address as your previous one.
Of course, I can delete your current ID, but that will make all of your previous message anonymous as they will lose the link to your ID that no longer exists. As such, I would be reluctant to do that without an overwhelmingly good reason to do so. That would make any messages you posted on the BOI appear to be anonymous.
In the new message board system I will going over to sometime in November, I will have the capability of changing user IDs easily.