Network mapping

We have a WIN2k workstation and our goal is to be able to map a drive letter to an AS400 server. We can ping the IP from the command prompt. But it does not show up in Network Places or show up using Find Computer when we enter the IP address of theAS400. We have a WIN98 PC with the same exact setup and it pings as well as maps to the IP address of the AS400 successfully.
What do we need to do different with Win2k?