It took me a second, but I found the config file to be modified. It was at C:\Users\<user>\AppData\Roaming\UFOAI\2.5\base in case anyone else needs to modify it. I also had to extract default.cfg from C:\Program Files (x86)\UFOAI-2.5\base\0base.pk3\0base\ and place it in the same directory, as well, otherwise the screen would hang.
So far, I've been able to get to the screen where the game asks me to confirm my name and language but it won't recognize the mouse clicking on any buttons. However, this is measurable and significant progress, and I'm okay with that!
In case anyone comes along after me, feel free to make use of my headaches and the most excellent help from Dark Rain and Norby. (I'm currently raising a glass to you, Norby. Thank you!)