I wanted to say, that there is no way, to stretch that tiny game box, but I actually find a solution, just right now ! Can you believe that ? If only I find it earlier...
Well, what you need to do is:
1) create an shortcut of a game icon, called "Game.exe"
1.1 you need to right-click it and down there you'll see that option, create shortcut
2) set a run parameter in shortcut
2.1 press right-click on shortcut, and click on it's properties
2.2 press to "shortcut" button in a top part of context menu
2.3 find a line with the inscription "window", down there
2.4 choose from regular window to expand or stretch to full screen (I don't know how it will be looked on your language)
2.5 press ok
3) run the game
3.1 press alt+tab couple of times, at least you need to full screen your game 2-3 times and then, it will be looked a bit shitty, but stretched almost to full screen game
There are pictures on how to do it and the result, for some reasons
Hope that is what you need