Samba 2.2.2 and user security

[Peter Erickson]

I actaully have a couple questions regarding this.

1. Is it possible to access a share and if the user enters a username which
   is not in my smbpasswd file, they automatically use the guest account OR
   samba assumes that they are guest unless they enter in a correct username
   and password?

2. With user security, it is possible to be able to browse which shares are
   available without actually entering a username and password? With my win98
   machine, I cant even look at the shares that are available from Samba when
   those shares allow guest access.

Thanks in advance.