Here are the programs needed:

GZDoom. This is not a guide for how to set up or run GZDoom or the games. There are other guides out there to help you with that.

A Batch file to EXE file converter. If you Google "Bat to exe converter", you will find one.

Notepad.

1) Create a new Notepad file.

2) Type this:


Replace YOUR PATH TO GZDOOM with your file path to the GZDoom folder

Make sure to include the two quotes with nothing between them after START, it's part of the formatting of that command. (It's for the window title of the cmd.exe window, but this window won't even be shown, so it's pointless to give it a title.)

For more custom command line arguments for GZDoom, look here[zdoom.org]

3) Save the notepad file as "dosbox.bat" and close Notepad. Make sure that the file ends in ".bat" and not ".txt".

4) Open the Bat to Exe converter program.

5) Click the three dots to the right of the "batch file:" line, and select dosbox.bat

6) Click "Compile" at the bottom. It will make an executable file named "dosbox.exe"

7) Go to the Steam folder for Heretic Shadow of the Serpent Riders and rename dosbox.exe to something else (I renamed it to "doxbox_REPLACED.exe"). You could also delete it if you want. In fact, you could delete everything else in this folder if you aren't going to run the dosbox version, except for HERETIC.WAD if you are using it for GZDoom.

8) Copy and paste or move your created dosbox.exe to the Steam folder.

9) To prevent Steam from automatically "verifying" dosbox.exe and replacing it with the official, original executable, right click your created dosbox.exe and check the "Read Only" box at the bottom of the window. This way, Steam won't be able to change it.

In your GZDoom folder, I recommend creating a text document called "autoexec.cfg" and pasting the following inside it to have helpful quick-use buttons for the healing item. You can change the Q key to whatever you prefer, but make sure that key isn't used for something else in-game. You can look as this wiki[zdoom.org] to see other custom quick-item bindings you can make.

The "m_showinputgrid -1" is to disable the on-screen keyboard that pops up if you have the mouse enabled in the menus and you try to save by clicking on a save file name. I find it annoying.