Can You Delete an Account on a MacBook?by Avery Martin
Deleting unused user accounts on your Mac can free up disk space. Whether you've created user accounts for family members or to divide up your work space, you can delete any of the accounts that you no longer use. However, you may not delete the only administrator account. If only one administrator account exists on the computer, you can either change one of the other accounts to an administrator account or create a new administrator account.
Click the Apple menu and select "Log Out" to log out of the account you want to delete, if necessary. You can't delete a currently logged in account.
Click the "System Preferences" icon located in the dock using an account with administrator privileges.
Select "Users & Groups" from the System section.
Click the lock icon and provide an administrator username and password, if prompted. Click the open lock button.
Select the account you want to delete from the Other Users section of the sidebar.
Click the "-" button to remove the account.
Select to “Save the home folder in a disk image," "Don’t Change the Home Folder" or "Delete the Home Folder.” Additionally, you can select the “Erase home folder securely" check box to securely remove the folder.
If you delete a user account with a home folder stored on a separate partition or disk from the operating system, you won't get a prompt to save or delete the folder. You must manually delete the user folder.
If you need to set up another administrator account, select the user account in the "Users & Groups" section and check the "Allow User to Administer This Computer" box.
Information in this article applies to OS X Mountain Lion. It may vary slightly or significantly with other versions or products.