make sure the guest account is enabled in start > programs > administrative tools > local security settings. the tree for this is "security options".
also make sure that "allow network access" is also enabled for the user "everyone" in local security settings. the tree for this is "user rights assignment".
again, make sure that "simple file sharing" in "my computer > tools > folder options > view" tab is DISABLED.
then, everytime you share a file or printer, make sure that the amount of users allowed is "maximum", and that permissions includes the group "everyone".
unfortunately, with this method, files that are shared are usually not viewable in network neighbourhood. you have to "view workgroup computers" and select the computer that you wish to access.