Can't see other devices on network

After a motherboard replacement I can no longer "see" my 2 XP computers or my NAS in Windows Explorer. Additional Info: While Explorer only shows the local machine, the map in the network and sharing center shows ONE of the 2 XP machines. Mapped drives on the 2 XP computers are accessible from the W7 machine The XP machines can "see" / access the W7 machine. Cisco Network magic running...