That problem usually occurs when you download a version of the game. Most torrents out there supply the international version of the World Adventures expansion pack, and if you live in the US or another region and have an actual version of The Sims 3 game installed (or a downloaded version, whichever) that does not have the same region code as the one you downloaded, you will get this error. Someone on one of the online forums took a screenshot of it, I've attached it to my post for you to see:
Before you do anything, make sure your The Sims 3 game is fully patched. Then try to run the installation of the World Adventures expansion pack again. If this didn't work, please read on for more instructions.
Now, first off, some more information about regions. There are 7 regions in all. The US and Canada are 1, Europe and Greenland are 2, Thailand and Indonesia are 3 and so on. What you want to do to resolve this issue is to match the region of your Sims 3 game to the region of the World Adventures expansion pack. Since the World Adventures pack, as mentioned, is the international edition, you have to change the number to "2". You can change it by following these steps:
1) Open your Start menu. Select "Run ..." and type in "regedit" to open your computer's Registry editor. Working within your Registry is very dangerous and could harm your computer, so before you start changing the appropriate values, be sure to make a back-up of it. You do this by going to File » Export. This will make a back-up copy of all your Registry information, and should you get into any trouble, you can simply import that file to restore the Registry back to its proper values (repeat this step, and instead of selecting "Export", press File » Import).
2) Navigate to: H-Key-Local-Machine\Software\Sims\The Sims 3.
3) Double click on SKU to edit this value, and change the number that appears there to "2".
Now you can run the installation again, and you should have no problems
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