ok i dont know who can open these and if you can change them or not but acouple of my friends found out how, its in chinese so i cant read but if you go here and download the file there, you can open c3 files, i dont know if this is useless or helpfull in anyway i just would like to share this with everyone else so we can better ourselves and the people around us.
Please if you have any knowledge on opening of c3 files or changing of the sort please post here