Several things need to happen. First, you need to edit the smb.conf file. This is the samba configuration file that allows certain hosts/networks to access the shared contents of your hard drive. You also might want to enable your samba server/client setup in the server options. The file itself is pretty self-explanitory, on what snippet of code does what, however, there is a good link out there for stepping though the smb.conf setup http://www.samba.netfirms.com/smbconf.htm
Next, you need to make sure that you edit the firewall settings of Linux. For starters, you might just want to disable the firewall completely to make sure that there is nothing hindering you. Then, as you see that everything works, slowly increase the security level and make sure that you allow incoming connections. Finally, you might want to edit the iptables (or create your own). There are some good sites out there, however i don't have them available to me at the moment.
Hope this helps,