Hello,
since nobody has written anything useful about this package, let me be that person.
About the game:
https://en.wikipedia.org/wiki/Diablo_(video_game)
0) Legal stuff
You can no longer buy a copy of Diablo 1 from Blizzard and their associated providers, the game does not come with a CD-key to be used on Blizzard's website, and there is no paid digital download option. According to Jurannok, a Blizzard representative on their Support Forums, the game has been discontinued and Blizzard has no current plans to update it or start selling it again. Sources:
https://us.battle.net/forums/en/bnet/topic/13595100072#post-2
https://us.battle.net/forums/en/bnet/topic/14611181553#post-2
As far as I am concerned, that makes Diablo 1 abandonware, so feel free to download this iso, legally.
1) Compatibility
This game can be run natively (without any mods or 3rd party utilties) on Windows 7 with color artifacts. By running the game in Windows XP Compatibility Mode and 256-colors mode, you can play the game normally. Alternatively, terminating explorer.exe process via the Task Manager after running the game will achieve the same result. The game will natively run only in 640x480 fullscreen mode with no option to change. There are ways to achieve better resolutions and windowed mode using 3rd party files/utilities.
2) Multiplayer
This game can still be natively played over Blizzard's Battlenet online service. After applying patch 1.09, you can select Multiplayer ->Battle.net and Create a New Account to log into. I tested this during my writing of this review, and I was able to log into US West gateway with no issues and Create a game. There were 0 listed games to Join, in case you're wondering. Apart from that, this game can also be played over LAN via Modem connection and the IPX protocol. Both of these are not used anymore, but there are tools to emulate IPX connection via TCP/IP (for example IPX Wrapper), otherwise 3rd party applications like Tunngle can be used.
3) Hellfire
This CD does not contain the Hellfire expansion pack. The expansion pack was developed by a different company and while it adds new levels, monsters, classes and spells to the game, I never felt the need to play this expansion.
4) Mods
There are two game overhauls you should be interested in. Both offer full support for newer Windows versions, bring support for up to 4K resolution and eliminate the need for compatibility fixes. Sadly, both also completely change the original game.
--- The Hell 2 ---
This modification is in it's final development stages, according to its developers. It's a rewrite for the original The Hell mod for Diablo 1. I consider this overhaul the better version to play.
- Significantly rebalances the game. Makes the game harder, and improves the dark feeling of the game for me.
- Fixes bugs and glitches from the original game.
- Adds some good things from Hellfire expansion pack.
- Adds completely new spells, items, locations, soundtrack, new AI and more.
- !!! Has working multiplayer !!!
--- Belzebub and Tchernobog ---
This modification has been stuck in development for quite some time, with no info about it's completion. It's a rewrite for original Diablo 1, but isn't based on any other mod (afaik). I consider this overhaul the worse version to play.
- Significantly rebalances the game. Makes the game easier, the game feels more like Diablo 2 and kinda loses the dark setting for me.
- Adds completely new spells, items, locations, soundtrack, and more.
- The 'Belzebub' version is the more finished version, but it can only be played in Single Player mode.
- The 'Tchernobog' version is the buggy and unfinished version (missing all quests, for example), but it works with Multi Player mode. The two versions are incompatible with each other.
Should you choose to play one of the mods, you might be able to get some support on their respective discussion forums.
Hope this helps.