If you have the game installed in C:\ProgramFiles\....... then that is why you can't see your nwn.ini.
When you look in your Neverwinter Nights Diamond Edition directory, if you have a TAB in the explorer bar at the top that says Compatibility Files.
then that is where you will find your nwn.ini
Disabling the intro movies is not a priority, as they are not stopping you from playing.
But getting the game out of ProgramFiles is.
Uninstall the game.
Go to Control Panel\User Accounts\Change User Account Settings & slide the setting to never notify.
Reboot
Disable your antivirus software.
Right Click on setup_nwn_diamond_2.0.0.15.exe & choose "Run as Administrator"
On the first screen where you have to tick to agree to their policies, you will see "options" down the bottom.
Click on that & change the install directory to C:\Games\Nevewinter Nights Diamond Edition. & then install.
Set your UAC back to the 2nd setting from the top & Enable you antivirus software.
Download & install the latest Nvidia Drivers from http://www.nvidia.co...s.aspx/73783/en-us
Do you know your screens native resolution & refresh rate?
Also which Processor you have.