You might not like the answer, but the Enhanced Edition should be out soon on GOG, it should run perfectly on modern machine/OS.

As for the Diamond Edition on Win7, have you tried compatibility mode?

So the answer is to pay twice what he paid originally for the same game. Post more information. Where did you install it, did you install outside windows foldesr? Thats check number one.
Have you tried all the options under the right click compatability tab? Probably win xp, but try them out.
Also try the game sub forum, for instance:
https://www.gog.com/forum/neverwinter_nights_series/neverwinternights_diamond_and_the_64_bit_windows_7_os_not_working_please_help

It's interesting that it was you who didn't like the answer...

And yes sometime you have to pay again for things to work. Not always the only option, but it is an option :)

I would say that's a last resort though. There are plenty of things to investigate and try to get it working on Win7 before buying it again. There's no reason it shouldn't work on Win7.

Canadian person suggesting that people should buy canadian products for "problem solving". Time to get suspicious.

I know, eh? That's aboot the most unsubtle thing I've ever seen. Sorry aboot that. :P

Hahaha it's the Canadian version of the Buy USA act lol!

But back to topic, it should work.

I would do a fresh install, making sure I backup my save game, to make sure no files are missing.

First thing, without even knowing what your system is: do not start the game from it's launcher. Go into the games folder and run the game directly from the .exe, not the launcher .exe Whilst you're at it, it wouldn't hurt to make sure you right click on the .exe and set it to admin rights and XP compatibility as well.

That is usually the problem with crashing on start up with this game.

As for all the graphical problems you will probably have, especially if you're using an AMD card, that's a different subject and is caused by the modern graphics drivers having some functions removed that were deemed obsolete. Unfortunately NWN actually uses some of those functions that have been removed.