If you're not already on the windows 8 start screen press the windows key. Scroll across to pc settings, click on it and select control panel from the bottom of the left hand panel. In the top left and corner of the control panel select "large icons" from the view by pull down menu Click on the recovery icon and select open system restore. Hopefully you haven't turned it off and you will have the option to select from a number of dated restore points. Select one which you know predates the problem and follow the instructions to restore to that point. If you are told that system restore is switched off then we have just eliminated one possibly easy solution as not being available!