It is located in appdata/monsterboy/sys.dat
Topic on Talk:Monster Boy and the Cursed Kingdom
If you want to try, you can use any text-editing program, such as Notepad.
Be forewarned, it may end up looking like nonsense (as in "$#^@jhkj14#@$") not because of Notepad, but because the file was not meant to be read by a human being, but by the game.
It may be perfectly-readable to a human, but I wanted to warn you just in case.
I just opened it up. It's a bunch of binary garbage, so it probably won't be useful/editable to anyone who doesn't know how the information is encoded.
Too bad. Thanks Baron.
Thanks Expack3. I just wish the game gave more detailed graphics options.