This worked for me:
- Right click on start.
- Click run.
- Type msconfig
- Click the "Services" tab.
- Uncheck the "Advanced System Care 11" service.
- Click ok.
- Click "restart your computer".
- Update KB4103721 as normal. re-enable the service is you want.
Confirmed as a fix on both of my machines with this issue.
Or short answer? Uninstall Advanced System Care 11 and reinstall it after you update windows.
Let me start by saying @SamuelKing2 is a genius as he found the missing piece I have been looking for--what software conflict does this update encounter?. EVERYONE ABOVE WHO HAS ENCOUNTERED THE "BLACK" SCREEN DURING THE UPDATE and who are running IOBit
Advanced System Care 11 NEEDS TO PAY ATTENTION AS **THIS WORKS**:
A recap of the issue: when KB4103721 starts it's install, it completes 30% of the setup before it does an automatic restart. When Win10 tries to complete the restart, it "hangs" with a black screen (and a constant spinny icon) until the end of time (or
your patience). For @SamuelKing2 (and myself), the problem is the KB4103721 and Advanced System Care 11 service do not play well together. The following summary provides a path to happiness.
If you are currently with the "black" screen, get your PC into Safe Mode (many ways noted above, but I use three power buttons to start, then push and hold the power button when the initial boot screen starts; after the third time, it will go into Advanced
Configuration and you can follow above directions to get to Safe Mode)
When in Safe Mode, do the msconfig update noted above, which will disable Advanced System Care 11. Then do the restart. Hopefully, this will continue the KB4103721 (last 70%) of the installation. If not, have your Windows Update try to do it again...it
WILL be successful when it does the update.
When Windows Update gets happy, then go back into the msconfig instructions above and re-enable Advanced System Care 11. After a restart, you should be as happy as you can get with a Windows 10 computer (varies by user, of course).
You're welcome! :)