Hello.

Headline asks it already. Can I download my order on several different PCs? Is there a limit to how much I can download it?

Let me reassure you before hand, it's not that I want to distribute the game to all my friends. They don't care about it. It's just that we have several laptops around home, and I skip from one to the other, being the youngest (and in the army, so I don't have need for one).

In GOG own words:

"Once you download a game, you can install it on any PC and re-download it whenever you want, as many times as you need, and you can play it without an internet connection."

Thanks. While I'm at it...

I'm downloading it right now, and started playing Medieval in the meanwhile. Once I quit Medieval, I saw that the download was still running, but it held a message that it had a problem downloading some file it didn't describe.

Is that problem dealt with, since the game is still downloading?

are you using the gog.com downloader? If so, I've never seen that error before, but you might want to try using a different download manager and downloading the files manually, as there are a lot of problems with the gog.com downloader right now. Also, you should only need to download once, then you can copy and paste the installer and archive files to multiple pc's, if your worried about the downloads taking time.

Link me please to a different downloader?

You can install games limitless times on any PC with Steam, so of course you can with GOG. You can just select "download with browser" to download it as you would any file off the internet. Just do what you did before to download it, but this time don't click on "download using GOG downloader", click on the other option. Unfortunately doing it this way means you have to download the game in one go - you cannot resume if you stop it partway. If the game is a pretty large download, this may be a problem if you have a slow or unstable connection.

Another question.

Where's the CD key located?

Games come with generic keys already included and at no point during installation you should be asked for CD-Key.
Some games however require unique key for multiplayer purposes. For them you need to contact support directly, but that information can be found at GOG game page, if applicable.

http://www.gog.com/en/support/neverwinter_nights_diamond_edition/online_play_in_neverwinter_nights_diamond

About the cd keys, do I need to buy multiple copies if I want more than one cd key (so that we can play LAN)?