- Turning off shadows completely will likely help quite a bit (point lights terrible).
- set the affinity of the game to 1 core through the task manager(right click on the application -> got to process -> right click on process -> set affinity).
- Depending on your graphics card, turning on v-sync might help. Some have said that the opposite is true though, and by turning v-sync off and turning on tripple buffering apparently results in the same image quality with better performance.
- If your computer has been running for a while, try rebooting.
- There are some features in the client extender that help with frame rate.

I think that's it...

Fyi you MUST have antialiasing to play the last part of the oc or you can’t fight the shadow avatar witch would become a game breaking bug.

I used this guide when I had a much slower computer, and it helped. It's kinda big. You might skip to page 5 if you don't want to read every word.

http://www.tweakguides.com/NWN2_1.html

What do you mean i have to have antialiasing?

Take a look at this screen.

so should it be set to the x2 setting then? or 0?

You didn't tell us what system | g-card you have so It's up to you but the technology didn't really take off so a modern g-card probably doesn't have the software for it and that’s an extra load on the cpu. On the other hand older g-cards do have the software to run it and might as well have the pretty shadows since it doesn't hurt their performance.

To be clear, you MUST have it for the shadow avatar fight but that is about 2 minutes at the final stage of the game so many people with advanced cards simply turn it on for that fight and the last shadow king encounter but leave it off for the rest of the game.