my computer has been 'installing' windows 8.1 update for hours now, how can I stop it

[WPCentral Question]

update 54 has been 'installing' for hours, i CAN'T USE MY COMPUTER

 

[Topshoeter]

I had this on my Yoga 2. Press the power switch for a few seconds to turn the computer off. Restart and it should finish updating.