Windows 10 freezes at downloading 99

So take a moment to compose yourself, keep your finger away from from the on/off switch, and follow the steps listed below to get it moving again... 

How to fix a stuck Windows 10 update

Step 1. The tried-and-tested Ctrl-Alt-Del may be a quick fix for an update that's stuck on a particular point. This function will allow you to access the login screen, and sign in as normal, but if not, further action may be required.

Step 2. Restart your PC. Resetting your PC mid-installation is a cardinal sin and expressly warned against by manufacturers, but if your update is genuinely stuck then you haven't got a lot of options. Use your computer's physical power or reset button, and remember that you may have to hold it down.

Step 3. Boot into Safe Mode. Accessible from the Startup Settings menu, this mode disables everything but the absolute essentials Windows needs to run, ensuring that any software conflicts that could be interfering with the update are removed. After the update installs, you can restart Windows to exit Safe Mode.

Step 4. Perform a System Restore. In order to safeguard against this type of thing, Windows will usually create a restore point just before applying an update, so you can roll it back if there are any problems. You can access the System Restore function from Safe Mode, or from the Advanced Startup Options if that doesn't work.

Step 5. Try a Startup Repair. A more in-depth fix than just doing a System Restore, the Startup Repair tool (also accessible from the Advanced Startup Options screen) can sometimes fix underlying issues that may be hampering the update process.

Step 6. Perform a clean Windows installation. This is pretty much the 'nuclear option', but if all else fails, you may be forced to simply erase your previous copy of Windows and simply start from scratch. Be warned, though, that this will erase your entire hard drive, so make sure that any vital data is as thoroughly backed up as possible beforehand.