If anyone is looking to replace or get spare computers, a site I really like is LaptopsDirect. To play NWN nicely you can get a nice pc or laptop for a 100 to 250 budget easily.
they do higher end stuff too priced nicely, especially if refurbished;
For example, i just picked up;
Processor - Intel Core i5 550Na - 3.2 GHz
RAM - 8 GB
Hard Drive - 2 TB
Operating System - Windows 8.1 (free windows 10 upgrade)
Optical Drive - DVD-RW
Graphics - NVIDIA GeForce 705
(for Euro 480 including delivery from UK to Ireland)
I'm not interested in high end gaming machines, it was for my brother. However, in terms of getting a machine to play NWN nicely, there are lots of great options, especially if you look through their refurbishes pc and laptops. Ive bought from them a few times and never a problem.