Do you have an Nvidia GPU card installed? Did you, or Windows, recently upgrade the GPU card drivers? If so, I'd try getting in via safe mode and reverting to or reinstalling the previous driver version. The current Nvidia drivers are causing black and white flashing screens at startup for a lot of users.
Once you get the driver working properly, do this:
Do you have an Nvidia GPU card installed? Did you, or Windows, recently upgrade the GPU card drivers? If so, I'd try getting in via safe mode and reverting to or reinstalling the previous driver version. The current Nvidia drivers are causing black and white flashing screens at startup for a lot of users.
Once you get the driver working properly, do this: