To solve this I tried to simply rename the user in User Accounts. However, all that does is change the appearance of the username in the Start Menu and User Account screen. The user folder retained its original mistake. I finally had to create a new administrator user with the right name, delete the user with the mistake but keep that user's files and transfer them to the new user. What a mess; all from one inadvertent key stroke.
Does anyone else have stories of similarly stupid, seemingly minor mistakes that cost you a lot of time and aggravation?