"Working on features // 100% complete" stuck, can't reboot

Question

I booted my Windows 8.1 machine up as normal this afternoon, after having shut it down normally the night before. While booting up it got stuck with the following message over a blank screen of my system colour:

Working on features

100% complete

Don't turn off your computer

Holding down the power button makes the fan and screen temporarily turn off, but pressing power again just returns instantly to this screen.

Researching this I've learned:

• This sounds like a common problem
• There are lots of different suggested approaches to fixing it, most are complex and seem to have serious side effects, and I can't find any clear steer on which of the suggested approaches to favour and why
• I can't find anything on what causes this error, what it means, or how to prevent it happening again
• At least one person had their machine stuck at this point for over 8 hours never resolving itself, so it sounds like just waiting isn't an option.

Other notes - the machine is a Wacom Cintiq Companion 2 (high-end work tablet), it's relatively new, and nothing unusual happened last time I used it. I've removed all peripherals such as a usb keyboard. I'm not aware of any system updates having happened in the last 24 hours.

I'd like to:

1. Understand what on earth is going in here
2. Know how to fix it with minimal side effects
3. Know how to avoid it happening again

Answer 1

Seems to me that you enabled or disabled one of Windows' features. You can do that by launching Control Panel and selecting Add/Remove Windows Features.

If you didn't do it then maybe a third party app did it. These usually take longer than normal Windows Updates. Try to remember whether you installed something before shutting it down.