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[Guest]

[steamid]_user_settings.cfg is not a file on my computer. Of course I used my personal steam ID.
The only things in /Main are _110000103DED3C0, Default, hlp.log, and hpl_update.log. There is a file in my steam location for SOMA thats called default_user_settings.cfg but that file has no option for fullscreen or windowed. I've verified my files, so I have no idea how to obtain the .cfg file you speak of.