First of all thank you for your help. Now to answer your questions.
> I assume that you are using an 32 bit Nim installation?
Yes, but before that I used 64 bit. Differences invisible.
> Is the chess game running for you?
Yes, a couple of fixes and it worked. If you want I'll write more detailed.
> If it really is Windows -- which gtk version, which windows, and how did you
> install GTK3 itself?
Windows 7 x64, gtk3 (3.20). Installed with Msys2.
glib except int32
NEd compiled. But is not completely working. I'll try to fix it. Anyway, thank
you again.