fedora miss one important parameter in samba config file: "map to guest". default security for samba service is "user" but windows machines unable to connect as guest without "map to guest = bad user" defined parameter. http://tech.waltco.biz/2008/01/26/private-and-guest-no-password-prompt-samba-shares-with-securityuser/
The 'map to guest' user option is supported.
i ask to add this parameter as comment in default smb.conf. for easy system montain. (i waste about 4 hours before find a solution)