These instructions worked on Windows 10/11 at the time this gist was written, on both AMD and nVidia, but that may have changed since. If it's not working for you, I may be able to help, but no promises.
Generalized Steps
- Download from Steam. (GOG also works, but the launch option bits would be different.)
 - Right-click in Steam, go to "Properties", then under "Launch Options" put: 
-nocolorkey -sortbyz -nointro -32bitand then close properties. - Download dgVoodoo2 latest release (currently: https://github.com/dege-diosg/dgVoodoo2/releases/tag/v2.82.3)
 - Unzip dgVoodoo2 somewhere and navigate to that folder.
 - Inside the dgVoodoo2 folder, copy 
dgVoodooCpl.exe,dgVoodoo.conf, and everything fromMS\x86into the Darkstone folder. (You can get to the Darkstone folder by right-clicking in Steam, going toManage -> Browse Local Files.) - From the Darkstone folder run 
dgVoodooCpl.exe. - On the 
"General"tab, in the"Appearance"section, change"Scaling mode"to"Stretched, keep Aspect Ratio". (5th from the top) - Go to the 
"DirectX"tab. Then change"Resolution"from"Unforced"to"Max ISF" - At the bottom of the window, click 
"Apply"at the bottom, then"OK". - CRITICAL STEP Leave the Darkstone folder. You can just browse one level up to Steamapps, but the game WILL NOT START if you are in the folder.
 - Try starting the game in Steam, it should work.
 
Running Windowed As a warning, Windowed mode may fight with Windows if you're scaling your desktop. In that case, you can either deactivate the scaling for Darkstone (instructions below) or change the scaling in dgVoodoo2).
- Open 
dgVoodooCpl.exein the Darkstone folder. - On the 
"General"tab, in the"Appearance"section, change the radio button to"Windowed"and the scaling to"Unspecified". Make sure"Keep window aspect ratio"and"Capture mouse"are both checked in the"Miscellanneous"section. - On the 
"DirectX"tab, in the"Behavior"section, make sure both"Application controlled fullscreen/windowed state"and"Disable Alt-Enter to toggle screen state"are unchecked. Change the drop down in"Resolution"to something you'd like, I suggest trying2xfirst, and go up from there. - At the bottom of the window, click 
"Apply"at the bottom, then"OK". - CRITICAL STEP Leave the Darkstone folder. You can just browse one level up to Steamapps, but the game WILL NOT START if you are in the folder.
 - Try starting the game in Steam, it should start full screen, but as soon as you click something in the game it should window itself.