I recently came across a problem with a new Windows 10 install where included apps (Calculator, Photos, etc) would not launch - at times even the Start Menu wasn't working. There are many possible solutions to this, though based on comments, many of them either don't work or even make the situation worse.
What worked for me was to check and fix permissions for the following:
In regedit.exe:
Right click on HKEY_Users and select Permissions...
Make sure that "All Application Packages" exists and has Read Permission.
Repeat for HKEY_CLASSES_ROOT
Expand HKEY_LOCAL_MACHINE. Check the subkeys HARDWARE,
SAM,SOFTWARE,SYSTEM. Make sure that All Application Packages has the
Read permission.
Other possible solutions are offered in this MS post.
