Maybe this post from that thread cuts though some excess.
Wilhelm II. said:Hi,
so i will explain the problem with the German Edition of Victoria.
During installation of the german version he needs a data3.cab file , which does not exists.
So you can only install proper in english!
Not so fine if you've bought it in german and also want to play it in german!o
The solution for it is to run the english install an then you have to edit the registry entry of victoria(search the registry for Victoria) or search this HKEY_LOCAL_MACHINE\SOFTWARE\Paradox Entertainment\Victoria in your registry.
There you will find an entry which names lang and the value is English. So now you have only to change the value to German.
Now you have the german version!
That sounds good so long, but the game is still in english(buttons,text ect).
Now you have two possiblities.
You can take the 1.02 german patch and install it or second you can take these files of improved german translation
(not mine
-> find it here: http://stonyroad.dyndns.org/phpbb2/viewtopic.php?p=7871
So thats it now you have a german version of VICTORIA
Greets