I have now made a tutorial on how to install and configure the 2006 PC version's ISO. It is the disc version of the game that requires mounting and installation as well as patching and installing the Style Switcher mod if you wish. Here's the tutorial on how to make it work:

The only differences I've found compared to the Steam version are that it has a visible exit option in the main menu and the M8 acid saps the player's health at the same rate as the other versions.

If you have any questions, please ask them in the DMC speedrun community Discord server: https://discord.com/invite/yhJdCHm