Hi running windows 8.1 Enterprise 64bit (old-I mean i have to update it from windows update every time I install it) Galaxy GTX 660 I5 4430 4gb kingston ram AsRock b85m Seasonic 500w power supply Samsung s19b300 monitor My issue started months ago when I was about to open a game and power suddenly cut in my home and after this my screen resolution always at low. when I manually edit resolution to high I see a little bit horizontal and vertical things then I reinstalled windows 8.1 and let windows install drivers and everything worked fine and after some days the issue come again after restarting and I can see a yellow sign beside GTX660 in device manager and when I install driver It doesn't work. I did reinstall windows 8.1 several times and its the same every time. I live in developing country so power always cut in my area. My question is I want to know if this is a software or a hardware issue ?