I didn't get very far and gave up. Put the file I got from the computer into the box that changes the world state and opens up the ground floor and basement but couldn't figure out what to do.
Judging by the above comment it involves editing the game files. Says find BOX and read newfound content and there's a file named BOX with a shard item I can't open because I don't have a program and I'm not paying for one and in the same file as the BOX file there is a ITEMS.rar I also can't open and also am not willing to pay for.
So I gues that's the end of the game for me.