Recently i tried to change the windows theme, then when it is changing the screen goes grey and I cant do anything but just force shutdown. Then when I turn on my windows back, it cant even start. It stays on a black screen. I tried to do a system restore via revovery mode and but i got an error 0x80070005. Then I tried to boot in safe mode but the screen is still dark. What should I do now? I have a lot of important files on it. I cant refresh and reset my windows 8.1 since i got no CD.