Fix for “critical error” Start menu and cortana aren’t working in Windows 10

1. Press ctrl+alt+delete on your keyboard
2. Click on “Task Manager”
3. Click on the “File” menu in the top left
4. Click on “Run new task”
5. Type in MSCONFIG
6. Click OK
7. Click on Boot Tab
8. On the bottom will be a section called Boot Options, check “safe boot” and select “network”
9. Click “OK”
10. Restart your computer
11. When it is rebooted and you get on the safe mode desktop, press ctrl+alt+del again
12. Click on “Task Manager”
13. Click on the “File” menu in the top left
14. Click on “Run new task”
15. Type in MSCONFIG
16. Click OK
17. Click on Boot Tab
18. On the bottom will be a section called Boot Options, check “safe boot” and select “network”
19. Click “OK”
20. Restart your computer

Basically your are booting to safe mode with networking and then rebooting normally.  For some reason this works for a lot of people.

When I tried this on a system that was giving the error I noticed that during the boot into safe mode, windows rolled back a failed update.  I don’t know if this is what fixed the problem or not but it is the only thing that I noticed windows doing during the procedure.  It fixed the problem for me so hopefully this will help someone else as well.