The firewall in SEP 12.1 is blocking XP and 2003 platforms' browsing of shares/computers. I can still map these shares as network drives etc. but I can only see VISTA and 7 clients in my network on my machines with SEP 12.1. SEP 11 does not have this issue as I still have a couple SEP 11 installed. These clients are managed from the server and I have verifyed this behavior by turning the firewall off.