Why re-install if you just want to personalize your user? Try what Tron suggested above.
I suggest you don't use capital letters for your new username.
Then to delete other users try:
sudo userdel <username you want to delete>
sudo userdel -r <username you want to delete>
(the last one will also the /home/<username> directory, so make sure to backup first files you possibly need.
Then create a password for your new user:
to log in as your new user in the terminal.
When you reboot you should be able to log in as your new user
(better don't delete any old user until you have logged in with your new user, just in case.)