1) (Only if you can't login or press f8) Keep force shutting down your device untill the repair screen comes up. Go to Troubleshoot - advanced options - Startup settings - select Restart - choose option 4)Safe mode. Once your pc starts up again, login and press the windows key + R and type devmgmt.msc and press enter. Once on device manager, select display adapters - right click the current one and select "Update driver" - "Browse my computer for driver software" - "Let me pick from a list of available drivers on my computer" - and double click on the driver of your choice. It works for me, as for I accidentally switched the driver to some unusable one.