Well this can be true sometimes when a game is uninstalled the files won't get deleted but there is a faster solution to restore your DayZ.cfg file. Since I did a few tweaks to mine I though I would reset this file. I deleted it and did a verify cache which did not work. I then started the game and a new DayZ.cfg file was created. I did need to reset the screen resolution and a few other graphics settings but it did do the job. WARNING: If you do this your screen will be running in a 640 by 480 resolution, the default for the game, your game will look horrible. It can be changed in game its just difficult to read the menus. You could also just alter the DayZ.cfg by hand to set your resolution.