Windows 8 is not working (why?)

My Windows 8 laptop has just been powered up for the first time in 1 year.
Now it will be displayed:
"Error configuring Windows updates. Changes are being undone
Do not switch off the computer."

It does not work (despite patient wait). What can I do to make Windows run again?

Either Windows 10 or linux. Windows 8 is partially with small Nils tiles

That can take hours, even days.

Well, play back your hopefully existing backup.
For such cases you do that yes.

Have it run all night. Now luckily it works again

Excellent! Maybe only the internet connection for the update download was sneak-slow… Who knows?