I found the following elsewhere on Microsoft community.
- Search for "Indexing Options" (under "Settings"). Open it.
- Search "services" (or run "services.msc") and find "Windows Search". Stop the service.
- Delete the Windows.edb file
- Click "Modify" in the already-open "Indexing Options" panel, then click "Delete and Rebuild" for the index. You can also specify a different drive to store the index on.
I have followed the instructions but need a day or so to discover if it is the culprit. Thanks for the help though.