1. I had run sfc /scannow already. It returned, “Windows Resource Protection did not find any integrity violations”.
2. I ran all three DISM commands. The results were "No Component Store Corruption detected" and "The restore operation completed successfully".
3. I upgraded to Windows 10 on July 5th. I created a system restore point on July 6th when I had completed the installation of all my programs. The first "Cortana - stopped working" application failure occurred on July 8th. Event Viewer>Administrative Events records the following:
Faulting application name: SearchUI.exe, version: 10.0.10586.420, time stamp: 0x57491ba1
Faulting module name: SearchUI.exe, version: 10.0.10586.420, time stamp: 0x57491ba1
Exception code: 0x80000003
Fault offset: 0x00000000001f7a57
Faulting process ID: 0x12a4
Faulting application start time: 0x01d1d94723d47aae
Faulting application path: C:\Windows\SystemApps\Microsoft.Windows.Cortana_cw5n1h2txyewy\SearchUI.exe
Faulting module path: C:\Windows\SystemApps\Microsoft.Windows.Cortana_cw5n1h2txyewy\SearchUI.exe
Report ID: 07519dc2-8b71-4b9e-9094-9cdfeb80b1a5
Faulting package full name: Microsoft.Windows.Cortana_188.8.131.52_neutral_neutral_cw5n1h2txyewy
Faulting package-relative application ID: CortanaUI
4. I ran System Restore successfully to revert to July 6th. An application error occurred for SearchUI.exe, version: 10.0.10586.420 as soon as my PC restarted.
Searchui.exe seems to have caused problems to many people. I guess my next decision is whether to carry out a reset, turn on Cortana or leave things as they are. The running of my PC is not afftected - it is merely the appearance each day of the application failure in Reliability Monitor that is off-putting.
I thank you for your constructive efforts to resolve this issue.