For some extra security you can add this:
PHP Code:
// ****** UNDELETABLE / UNALTERABLE USERS ******
// The users specified here will not be deletable or alterable from the control panel by any users.
// To specify more than one user, separate userids with commas.
$undeletableusers = 'X';
Above the // ****** SUPER ADMINISTRATORS ****** and change X to your userid.