The setup for any version is pretty much the same, so here's the
setup for v1.7, but use
HUv1.21z instead. The setup refers to webpages,
here they are for v1.21z (there will probably be a few minor errors). If you want to use D2SE, then you'll need a
D2SE_setup file for HUv1.21z.
Arimyth realm is hosting HUv2.1 currently, so to play v1.21z multiplayer you'll need to either play LAN games or join up with the
Discord HU Community. There's a good chance they'll have a link for a complete file tree of HU, just in case you've lost your discs, or are having trouble with getting set up.
If you're low on ideas for a character, feel free to ask the folks in Discord, or consider one of the
characters I enjoyed back in the day.
Here's a
list of files hosted by Arimyth, in case you need them. It looks like the thread for HU1.21 might not include the updates or multiplayer versions, but those are available.