The source code to Diablo: Hellfire, the expansion to Diablo by Synergistic Software

https://archive.org/details/hellfire_source

http://www.oldpcgaming.net/diablo-hellfire-review/

1. Install Visual C++ 6.0

   https://archive.org/details/MicrosoftVisualC6.0StandardEdition

2. Download the repository, switch to \src and open the workspace file DIABLO.DSW with VC++ 6.0

   There are two projects in the workspace: Diablo files (hellfire.exe) and ui files (hellfrui.dll)

3. From the main menu Build > Rebuild will create \Windebug\hellfire.exe and \Windebug\hellfrui.dll

   Run Z.BAT will create \WinRel\Diablo.exe using a makefile DIABLO.MAK (probably it's for a production)

1. To be able to run the game (\Windebug\hellfire.exe) you have to download and place HELLFIRE.MPQ and DIABDAT.MPQ (from original Diablo: Retail) into \Windebug directory

2. In VC++ project open Project > Settings, switch tab Debug and set option Working directory to full path to your \Windebug directory.

3. Build > Start Debug > Step Into will set break point on entrypoint function WinMain(..) in DIABLO.cpp.