When clicking on mask.exe nothing happens.
While playing with properties, I managed to get some kind of DRM error, but unable to recreate the error anymore.

Thing's I tried:
All sorts of exe compatibility settings.
KingsQuest8-Patch1.0.0.3 doesn't update.
Mask.exe already showing product version 1.0.0.3 from GoG installer.
4gb_patch.exe makes no difference.
dgVoodoo2
Moving everything to C:\SIERRA\Mask\

Anyway someone could update the game for newer Windows? Even if I'd have to pay something reasonable..

It's working fine on Windows 11 for me. Especially since Windows 11 is pretty much just a GUI update to windows 10. None of it's major components have really changed

Interesting.
Is your version from GoG?
Could you check the version of mask.exe?
Any tips on how you installed it?

I got it to work using YouTube guide Kings Quest: Mask of Eternity - Install Part 1
nglide allows 800x600
dgvoodoo2 does 640x480