Hey RustKnight, you're in luck! I have been tooling around with Visual Studio Express 2013 for Windows Desktop (available here in m$ "hard-to-find" section): https://visualstudio.microsoft.com/vs/older-downloads/
I used the "Concurrent Version System" version of IVAN, purported to be the last version the original devs worked on, linked here: https://attnam.com/projects/official/IVAN-CVS
Download the source, which is ivan-cvs.tar.gz (you can unzip this using 7zip). I unzipped it somewhere with a handy folder name like C:\ivan-cvs
Then I downloaded SDL 1.2 (not SDL 2.x) from here: https://www.libsdl.org/download-1.2.php
I downloaded the SDL-devel-1.2.15-VC.zip for Visual C++. I unzipped this folder into C:\ivan-cvs and re-named it just "SDL" (so now I have a folder located here: C:\ivan-cvs\SDL
Next I opened the IVAN.dsw (found in C:\ivan-cvs) with Microsoft Visual Studio
Click OK and it does the conversion step automatically, it will say it's no longer backward-compatible but you can ignore this.
IMPORTANT STEP: Once in Visual Studio, my very first step is to change the "Solution Configuration" in the drop-down menu to "Release"
Next I followed the incredibly well written SDL setup steps from https://thenumbat.github.io/cpp-course/sdl2/01/vsSetup.html
These steps are the same for SDL1.2 as they are for SDL2.0, except you should use SDL where they write SDL2 etc
Other changes were: I used absolute paths for the location of SDL, both the header files (where SDL.h is found) and the library files (where SDL.lib and SDLmain.lib are found)
IVAN is a little bit different in that the "Main" project (ivan.exe) is dependant on "FeLib" (a.k.a. the "Fatal Error" library - the original devs' custom C++ library). Simply follow the same configuration steps to both Main and FeLib. For instance, for FeLib, the Additional Dependencies can be found under "Configuration Properties- > Librarian -> General" and you can add
(This contrasts with Main, where this is done under "Configuration Properties- > Linker -> Input", as per the instructions in the SDL setup guide I linked).
You can press F7 now to build, but you will get errors. I made them go away by doing the following:
1. Added _USE_32BIT_TIME_T to "Preprocessor Definitions" which I found under Alt-F7 "Configuration properties -> C/C++ -> Preprocessor"
2. Added WIN32 and _WIN32 to Preprocessor Definitions (this seemed not ti fix anything, but I did this for superstition)
3. Replaced #include "afxres.h" with #include "windows.h" in Ivan.rc (seemed to overcome the "afxres.h not found" error, thanks to this answer here: https://stackoverflow.com/questions/3566018/cannot-open-incl...
4. I used absolute paths for SDL.lib and SDLmain.lib, like so:
Then I pressed F7 to compile and build. It magically builds IVAN.exe located at C:\IVAN-cvs. If you click on it to run, you will get another error saying SDL.dll not found. Copy SDL.dll from C:\IVAN-cvs\SDL\lib\x86 to the folder where IVAN.exe is and then open IVAN again. It will run the game.
Please let me know if you get stuck and I will see what I can do to help. If you're unsure about my VS configs, I can post screenshots if you like
Corollary: I wonder if Appveyor does Visual Studio builds in the cloud??