Originally Posted by CrazY.
I've managed to view some files of unknown extension in a text editor, try that.
If that doesn't work, it seems like that a file of .CSO format is basically a compressed .ISO, I'm not sure though. You could convert from CSO to ISO and open it with winrar, but you'd better just search on google "how to open a .CSO file"
It may also be a file strictly used in the engine that was used to make the game, in that case you are out of luck
Thanks for your suggestion，though it doesn't work. I think I'd better give up opening this file.