could be the video driver is not set or scripted to run the older needs of NWN.
since you say it is a new computer and i am assuming you are trying to run on the default graphics drivers provided. You may want to try NGOHQ.com or other sites like that for a modified driver. they typically alter scripts to enhance and increase quality or frame rates. To avoid spending too much time and having to become a video driver guru to solve this, assuming it is drivers, I would just try a few different ones and play with the settings.
good luck