If you want to rename an Account, open its Settings page, and enter a new Account name into the New Account Name field. Click the Rename Account button.
If there is no other Object with the same name as the specified new Account name, the Account is renamed and its Account Settings page should reappear on the screen under the new name.
You cannot rename an Account when it is in use.
If you are a Domain Administrator, you should have the Can Create Accounts Access Right to rename Accounts in your Domain.
You can move an Account into a different Domain, if you specify the new Account name as newName@domainName. If you are a Domain Administrator, you should have the Can Create Accounts Access Right for both Domains.