This error is caused by the Ogre.cfg file that was not created (you have Win7 and I don't have such a problem on Win 10) Find a file somewhere or in this message. Drag it to the "config" folder, then edit the screen resolution in it and hooray! the resolution has changed, but if you want to change something in the "Render System" settings, the game will crash. Change it in the same file. I hope my solution to the problem will help you.