According to other users and admins here the GOG version is compatible with this mod, but for some reason it won't work for me. When I click the mod executable the game will launch, but the intro video is choppy, the screen will flicker a few times, and then my computer freezes entirely and I have to do a hard restart.

Any ideas what could be going wrong? I'm on Windows 7, and my PC hardware is fine, as far as I can tell. ( Been playing the Resident Evil 2 remake lately, with zero crashes or freezes. )

Without the mod the game seems to work properly, but I'd really like to add some of the mod's enhancements to my playthrough.

Try to instal this mod into main folder of Diablo (default: GOG Galaxy\Games\Diablo) and then set .exe to compatibility with Windows XP service pack 2. You should launch mod with their exe (not by GOG Diablo launcher).

Did you try it with the original version (apparently it's included in the purchase), or with the fixed one?
Afaik you should use the former.

I installed it according to the instructions included with the mod, and also tried an alternate method, but both ended up with the same result, as described in my opening post. And yes, I did start it using the mod executable.

I guess I could try the compatibility settings. Is the mod known to be incompatible with Windows 7? Yeah, I used the original game folder, as I figured that's what the mod was developed for. I suppose I could try the other folder, just in case, but I doubt it would work.

I also tried a different method, using only the game's main data package, combined with the mod files, but the result was the same. The game starts, but the intro won't play properly and eventually the computer freezes entirely.

I'm not sure if it could simply be some video file issue? But the videos work when I launch the game without the mod.

The classic Diablo is incompatible with systems newer than Windows XP

Doesn't matter since Belzebub has its own executable which is made for newer Windows systems
(and also runs well in Linux via WINE btw).

So to sum it up, you have no issue with Diablo, only with the HD Mod?

If so, you should ask your question on the mod's forum, over there : http://awake.diablo1.eu.org/codename-belzebub-f3.html

Maybe I should simply wait and play it on my new PC, using either Windows 10 or Linux. :/

Did anyone here try it on Windows 7? I posted it here because the mod was mentioned here in several threads, and several users as well as GOG admins said it is compatible with the GOG version. Besides, I figured if someone knows a solution it would also benefit other GOG users with the same problem. That said, I may have to do some more digging through the mod's forum.

As with the other fella here today, try uninstalling and/or (re-)installing OpenAL and VC 2010 Redist. The problem you're having seems like the kind of thing that could happen if one of those two things goes awry somehow and finds itself in an incompatible state.

Yeah, I had a problem with OpenAL too I had to fix first, but got an error message regarding SFX suggesting it at least.

That's what has me puzzled -- Generally when a Windows component is missing or out of date, software will simply refuse to run and/or result in an error message. This complete system freeze, without any kind of error message, seems odd. And I haven't noticed similar behaviour on any other games or applications I've used lately. In fact, during all the years I've used Windows XP and 7, only a handful of games ever caused such severe crashes/freezes.
Hm, which version of the mod are you using? I got mine here: https://mod.diablo.noktis.pl/download Version 1.045

That is the exact version I am using.

I pretty much expected so. Perhaps it could be a GPU driver issue, or an out of date Windows component, as someone else suggested. At this point, I'm just about to say fuck it, and just play Vanilla Diablo for a while. Might try the mod again once I switch to my new PC, next month or so, so I can try it on Windows 10 or Linux Mint.

Does the mod improve the framerate, or is it always limited to 20-ish FPS?

it ups to 60 but it has features that I personally do not like.