Over the holiday weekend, I brought the hard drive home (an Iomega Home Network 500GB), plugged it in, configured it over the web interface from Dedalus. I named the drive Boylan, did a Go > Connect to Server... from Finder, and It Just Worked. The network drive shares files with the Samba protocol (a/k/a SMB, or Server Message Block), and Mac OS speaks fluent Samba.
Not quite so easy connecting from the Windows machine. I tried using the Iomega-provided Discovery Tool Home to mount the shared folders. The tool could find the drive and folders, but when I picked a folder and clicked the button, the tool popped up a dialog with the rather unhelpful message "Exception Error."
I fiddled with the port settings on the firewall that I have running on on Mulligan (Norton), but no luck. I disabled the Norton firewall and went back to Windows Firewall, but no joy again.
I started a chat session with a support rep from Iomega and learned the first secret: the Discovery Tool is just a GUI for Tools > Map Network Drive..., because that's all that the rep used to work the problem. Unfortunately, Map Network Drive... was equally unable to mount the shared folders, and provided no clue as to what was not configured correctly. He asked me to check some settings on the router, and at the moment I had a glitch logging into the router, so I had to close the chat session.
The next day I had some free time to do some searching, and I turned up a page of David Lechnyr's Unofficial Samba HOW TO that taught me the second secret: Tools > Map Network Drive... is just a GUI for the console command net use. So I tried
net use e: \\192.168.0.101\public
and I got back the message "System error 1231 has occurred." Finally a clue! More searching, and I found a nicely comprehensive list of System Errors and troubleshooting tips. The page for 1231 reads, in part:
...when we checked the Properties of the LAN, we found the Client for Microsoft Networks and File and Printer Sharing for Microsoft Networks were disabled.
I bounced off to the Properties sheet for my network connection, and indeed, Client for Microsoft Networks was disabled. I checked that box, rebooted, and much satisfied mounting of folders was mine. Furthermore, now both Boylan (the hard drive) and Mulligan (the laptop) show up in My Network Places under Microsoft Windows Network and the node for the workgroup.
So, while File and Printer Sharing for Microsoft Networks enables other devices to access shared external resources from the local machine, Client for Microsoft Networks works in the other direction—it enables the local machine to access external resources.