Windows update installation stuck?

1. Press Ctrl-Alt-Del In some situations, the Windows update(s) may be hung at a very particular part of the installation process and you could be presented with your Windows login screen after executing the Ctrl-Alt-Del keyboard command. If so, log on as you normally would and let the updates continue to install successfully.
2. Restart your computer, using either the reset button or by powering it off and then back on using the power button. Hopefully, Windows will start normally and finish installing the updates. If you're using Windows 10 or Windows 8, and you're taken to the sign-in screen after the restart, try tapping or clicking the power icon on the bottom-right and choosing Update and Restart, if available.
3. If you're automatically taken to the Advanced Boot Options or Startup Settings menu after restarting, choose Safe Mode and start Windows in Safe Mode. This special diagnostic mode of Windows only loads the minimum drivers and services that Windows absolutely needs so if another program or service is conflicting with one of the Windows updates, the install might finish up just fine.If the Windows updates do install successfully and you continue to Safe Mode, just restart from there to enter Windows normally. 
4. Complete a System Restore to undo the changes made so far by the incomplete installation of the Windows updates. Since you can't access Windows normally, try doing this from Safe Mode. See the link in Step 3 if you're not sure how to start in Safe Mode. During the System Restore, be sure to choose the restore point created by Windows just prior to the update installation.Assuming a restore point was made and System Restore is successful, your computer should be returned to the state it was in before the updates started. If this problem occurred after automatic updating, like what happens on Patch Tuesday, be sure to change Windows Update settings so this problem doesn't reoccur on its own. 
5. Try System Restore from Advanced Startup Options (Windows 10 & 8) or System Recovery Options (Windows 7 & Vista) if you're not able to access Safe Mode or if the restore failed from Safe Mode. Since these menus of tools are available from "outside" of Windows, you can try this even if Windows is completely unavailable.Important: System Restore is only available from outside of Windows if you're using Windows 10, Windows 8, Windows 7, or Windows Vista. This option is not available in Windows XP. 
6. Start your computer's "automatic" repair process. While a System Restore is a more direct way of undoing changes, in this case a Windows update, sometimes a more comprehensive repair process is in order.In Windows 10 and Windows 8, try a Startup Repair. If that doesn't do the trick, try the Reset This PC process (the non-destructive option, of course).In Windows 7 and Windows Vista, try the Startup Repair process.In Windows XP, try the Repair Install process. 
7. Test your computer's memory. It's possible that failing RAM could be causing the patch installations to freeze. Fortunately memory is really easy to test. 
8. Update BIOS. An outdated BIOS isn't a common cause for this problem, but it's possible.If one or more of the updates Windows is trying to install is involved with how Windows works with your motherboard or other built-in hardware, a BIOS update could solve the issue. 
9. Clean install Windows. A clean install involves completely erasing the hard drive that Windows is installed on and then installing Windows again from scratch on that same drive.