I just looked, I did not get Swedish. Does that mean you got sold a game which isn't even available in your language? That sux. >:-(

What JSZ means basically makes sense.
The best way to make sure not to change the filesize is to use the "overtype" function. There's a key for activating it on your keyboard.

Hope that helps. If you didn't use the overtype function before, best is you first get familiar with it in word or something like that.