samba - Nov 2003 - security = user , but no username asked?

Hi,
 
    I've been using samba for a long time with security=share, with that
any of my clients (w98 machines) could read/write any file on a public
share.
 
    Now I'm using security=user  but I still want to have a public share
that should be accessed by anyone without password. Using public=yes
guest ok=yes guest only=yes didn't worked. When I try to access the
share I still get a user/pwd prompt.
 
    there's any way to do that? I've read security.txt but could't
find
the solution.
 
 
thanks alot
thiago lima.