PowerConnect 5224 - delete default Guest login?

I'm new to these switches, but have used others in the PowerConnect line.  Is it possible to delete the default 'guest' login?  I realize it can be set to minimal access, but even that reveals too much about the LAN and VLANs for my tastes.  Setting the password to something else is better than nothing, but still lame.  How do I lock this down?

Thanks!