For your information:
I installed windows 10 pro this morning. Calibre is running well.
By accident, while checking if a pdf ifilter was present in the file types list for search (control panel, indexing options, advanced, file types), I discovered an epub ifilter. I changed its settings to "index file name AND contents" indexing. It then changed to "plain text filter". Indexing is still running. I'll report more when the indexing is finished.
