without knowing the physical layout of your LAN. Assuming from your statement that ICS is being used, it's likely file sharing has been turned off. Also check your workgroup names and disable any firewalls until the network is up and running.
I have a LAN with windows 2000 server and windows 2000 XP and Windows 2000 professional workstations. I am not able to browse the network from my network places to pick shared items.
Suprisingly, I am able to ping all machines in the network, internet connection sharing is working perfectly and emails as well.