I'm experiencing screen tearing while playing NWN Diamond Edition, purchased here in GOG.

I've enabled V-Sync in the settings. It's also enabled for this game on my Nvidia Panel. Yet I'm still getting tearing.

My specs:

Windows 7 Home Premium 64-bit SP1
Intel Core i5 4690 3.5 GHz
8 GB RAM
2047MB NVIDIA GeForce GTX 750 Ti

Any way I can reduce tearing? It doesn't look good.

My V-Sync does nothing either!

Check if other resolutions make a difference. YellowAries reported that he had problems especially with a HD1080 resolution (1920x1080).

You could try D3DOverrider (Comes with Rivatuner) to force V-Sync at a driver level. It works with Win 7.
http://downloads.guru3d.com/download.php?det=163

If you enable VSync you also need to enable Triple Buffering (it's pointless without it).

V-sync is hardly pointless without triple buffering, just lags a bit. :P
(DirectX based games don't support triple buffering at all, so it's basically like any DirectX game with v-sync enabled)

V-sync doesn't work for me either in NWN (using AMD HD7950) there is always some screen tearing. I have not tried to force it with the video drivers yet, let's do that now...
...and yes that works. I can successfully force V-sync with AMD Catalyst 14.9 WHQL, no more tearing.

The in-game setting doesn't work for me, but forcing it with the driver does work.