Yesterday I was playing on my computer and accidentally hit a button that said do you want to update your windows to 8.1. and

[Sophiadiamonds]

It was a black screen for a moment until the loading screen showed up so at first I thought it was normal, until it repeated and I could not press any buttons. I have a Samsung.

 

[Reyaz123]

It is updating your pc. It usually takes around 2 restarts to complete it, I had the same problem too and waited it out.