How to get Heretic to work on Windows 8 without downloading any sourcecodes or ports
So, getting Heretic to work on Windows 8 is not a long, nor difficult task. I'd like to point out that I did actually get my help from the internet, but I did have to improvise a bit.
First, go to OS (C:) > Program Files (x86) > Steam > steamapps > common > Heretic Shadow of the Serpent Riders > base
Right-click HERETIC and go to 'Properties' then set compatability mode to Windows 95.
Then, go to heretic.conf and open it with Notepad.
Change 'fullscreen=true' to 'fullscreen=false' and 'waitonerror=true' to 'waitonerror=false'.
Then, open dosbox.conf and scroll down to where it says 'waitonerror=true' and change it to 'waitonerror=false'
Make sure you save these changes and close the files.
Go to your Steam Library and go to Heretic: Shadow of the Serpent Riders and click 'Play'
If it still doesn't work, like it did for me, go to doom2.conf and change 'fulldouble=true' to 'fulldouble=false'
After this, it should all work.
Hope this helped you! :)
P.S. This will work in any game that uses DOS box such as Doom, Heretic, or Hexen