Well, I was looking forward to play this old classic on Win 8.1 but I can't because the game won't start properly. The music play, there is a process with the name "nwmain.exe" BUT :

There is no window to click on. The process seemingly runs in the background while there is no "main window" for the game.


Any fixes or should I not bother and uninstall?

Hm, I can run NWN Diamond on Win 8.1 without issues. Does this happen every time, even after rebooting your computer? I've had temporary issues with games not being shown in the taskbar occasionally, after I ALT-TABbed out of them. In those cases I call the task manager and double click on the running process instead. Have you tried that already, double clicking on the nwnmain.exe process in the task manager? Also, do you use the GOG shortcut or do you start the game directly with nwmain.exe from the game folder? It might be worth trying whether choosing the other way changes anything. Maybe also try to set it to "run as administrator" if it isn't already?

Try installing DirectX: https://support.gog.com/hc/en-us/articles/214063165-Neverwinter-Nights-Diamond?product=gog, maybe it's worth reading throug gog's support materials for NWN: https://support.gog.com/hc/en-us/articles/214063165-Neverwinter-Nights-Diamond?product=gog, or alt+enter on the game shortcut and try to play with compatibility tab.
Good luck.

Thank you very much for the answers, I will try your tips and report back!

Ok, thanks again for your help, I got it working by starting the nwmain.exe directy (I right clicked first for "start as admin", then as I wanted to test if it would work without admin, Windows prompted me for admin password, so it's already set internally.

Well, nice, I really appreciate the help!