Windows 10: What do I do?

So my PC is a bit older and recently it randomly decided to not work right being the windows os on my HDD and when I try to turn it on it says loading windows then tries to auto do an update that freezes on 15% then it tries to restart and I've waited 8 hours on that restarting screen for nothing to happen so I just shut off my PC and turned it back on to try again, it won't boot up windows and only tries to update this download it can't complete. And there isn't any buttons to close the update or anything either so that telling me something about a button won't help it's not manually done

:)