Lunarius_pro: Do you have NET Framework 3.5 and VC++ redistributable 2005 and higher installed (many 2000's games need them)? Also DirectX? It's just a suggestion...
NWN1 didn't require.NET Framework, made use of OpenGL rather than DirectX and - having been released in 2002, seems rather unlikely to need VC++ 2005...
Zahroc,
For a problem like this, I would suggest trying another OpenGL game or benchmark to see if that shows similar symptoms. If it does, then that suggests a general problem with OpenGL. If the other software works, make a backup copy of the opengl32.dll file in your NWN folder and then copy in the opengl32.dll file from the working game.
Another possibility is to check the Compatibility tab for nwn.exe and nwmain.exe (try disabling anything set to start with, then try running as WinXP).
If you have activated Controlled Folder Access in Windows 10, try disabling it (if that then works, you will need to configure an exception for NWN before re-enabling it).
You don't mention what updates you have applied to your Diamond version, so it is probably worth checking that you have added at least the
NWN 1.69 Critical Rebuild
