I spent an hour each day for the last week trying to get an XP machine to join a customer's Samba domain. Every time I tried, I got a message stating that the Samba domain was unavailable. Naturally, I wasted a lot of time trouble shooting Samba to see what was wrong. Turns out the XP machine had Symantec's personal firewall product loaded. Once I configured the firewall to allow SMB, I was able to add the machine to the domain. Also had to allow NetBios browsing in order to browse the network. Just letting you guys know so that you don't waste time the way I did.