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Change Language to English
To change language from game, you need to go to
"C:\Documents and Settings\USERNAME\My documents\Eidos\Batman Arkham Asylum\BmGame\Config". There you will find a BmEngine.ini. In this file, find the line "language=pol", and change it to "language=int".
About the other folder you mention, indeed, it was missing in my version too, I remember now.
This contains the messages linked to the program itself, like name in task list, or error messages. However, this has not been translated anyway (you can see that if you read this file with some notepad).
So all you have to do, is to duplicate the RUS folder there, rename it to INT, then change extensions of the files inside, from ".pol" to ".int", and it will work.