Normally, I just download my games from gog, launch them up and then they're ready to play.

This time, however, it seems as though I need my serial key, to which I don't know where to find it. Where do I find my serial key?

Edit: Nvm, it seemed to work after restarting my computer.

Cheers for that. V.Helpful. I was worried that GOG screwed up on that for a minute. :)

I was wondering about that myself at first. I was like: "I need to manually enter my serial key? Really?" I noticed a serial key was posted in my accounts page for the game when I downloaded, so I went there to copy it down just to have the game run without issue when I launched it for a second time. Weird. *shrug* Fine by me though if I don't have to fiddle with it.

I found the probable reason for the error and solution is actually quite simple. If you are using Win 7 (like me), just right click the desktop icon for the game, and select run as administrator. The problem seems to be the game is trying to register the serial number in registry and cannot do so under normal privileges.

How do you enter that key?
I need to use ctrl+alt+delete out of game as it blocks alt+tab to see the key.

the problem seems to be that the gog installer starts the S3.exe directly. the "The Settlers 3" shortcut on the desktop obviously starts the game in a different way, at least after that the cd key is no longer required.

I just went to my account page with the games list, clicked on settlers 3 and it shows the serial number there. You'll have to write it down as copy and paste doesn't work; make sure you include the hyphons.

This worked for me.

I'm finding it annoying that they seem to keep asking for the key every single time I start the game. I didn't mind copying it over the first time, but every time?

then something isnt right with your installation because its not required to type in the cd key ever. try the different .exe files in the directory, with admin privileges just in case.

HI there,

As what was explained in the solution happened to me. I was prompted to enter the CD key, but had saved it to a text file on my hard-drive so cancelled and exited the game. I then wrote down the key, to then go into the game and find that I'm now no longer getting the prompt, and therefore unable to enter the key.

I don't feel secure about this because the way the Settlers 3 "Copy protection" works is by altering things in the game, that are not obvious at first glance. For example, the Iron smelters randomly stop making iron, instead they make pigs. With this happening, its not possible to build an army!

Ideally I want to know (without spending hours playing to find out) if the game is actually in "genuine" mode and not thinking its a pirated game, and all kinds of weird things happening.

Hi,

If I'm not mistaken the copy protection was not dependent on the serial key, but only kicked it if a non-original CD was used for playing and/or installation (parts of the original CD were made "damaged" on purpose as part of copy protection). 2 things were altered: aside from the iron smelters making pigs which you mentioned (pig iron, get it?), the trees planted by foresters wouldn't grow properly, so the woodcutter couldn't cut them and they'd only take up space without providing any wood.

I have the CD and not the GOG version of this game, so I can't answer your question, however I'm almost 100% sure that the GOG version doesn't have this bug because:
Hundreds of users with gog versions have posted questions about the campaign on these boards. If they had the bug they wouldn't have been able to play the game. And at least one of them would have mentioned it.

I have buy the S3 at 10 min, i cant find Cd Key.
Some one can help me find it ?

You shouldn't need the CD key. Simply try starting the game again.