renaming sin.exe to quake2.exe. This is how I "fixed" the original patched up disc version. I'm now able to play Sin in "default opengl "mode on a Win 7 x64 machine (i7, 6gb ram, 560ti ) without issues and without nglide or other tweaks.

I have no idea how GoG configured this game so maybe this particular problem is fixed, just thought I'd share this just in case.

Enjoy Sin.

nVidia cards require you to turn on an obscure setting called Extension Limit to run Sin without crashing, and your drivers probably have a profile set to automatically do this for Quake 2.

This does indeed work, thanks! Do you perhaps know how to make a new or copy of the Quake2 Nvidia profile for Sin.exe to do it the 'proper way'? So that all shortcuts etc. remain functional? The current drivers no longer have the option to set that flag from the GUI...

I think the Nvidia Inspector program can do it.

Yep; it does thanks! Annoying that NVidia no longer grants access to the profiles out of the box.

Sticky this shit asap solved everyproblem i had with this game

This is pretty incredible. I was struggling to get the thing working fullscreen without screwed-up colors before even attempting to actually play it... I tried changing it to quake2.exe and next time I start it up, not only is that possible, but it plays an intro movie that I didn't even realize existed because the game apparently glitched and skipped over it before. Haven't actually played the game yet, but that's a heck of an improvement for just changing the file name.