Essentially, you can't. (Except for pleading privately with a mod or admin. Without a very good reason why, I wouldn't count on their complying.)
What you can do is disable this account, and open up another. This gets discussed here & there; being more of the what's-in-a-name variety myself, I can't say I've remembered any details on it. Search the forums for it some, it gets asked about quite regularly.
