Several facepalms in this adventure.
First was finding that I needed to enable NetBios on the Windows 7 machine.
While I was at it, I checked one of the W2K machines, (primary one with all sorts of shares on it), and turned on NetBios there too.
Rebooted, and while the other computers are not showing up in any of the network pages, doing a direct \\computername results in the associated machine opening up in a explorer window.
Going the other way, still could not find the Windows 7 machine on the network.
Issue was "homegroup" settings, needed to change machine to being in a homegroup, same workgroup name, and then while the Windows 7 machine does not show up in the W2K network, direct typing of the Windows 7 machine's network name and the shared folder results in the W2K machine being able to open the folder, plus with the bonus of being able to read / write the folder.
Hey, overall, this is a bit wonky, but it's working now.