Hi ccpjr,
By default, all of the most common files on your computer are indexed. Indexed locations include all folders included in libraries (anything you see in the Documents library, for example), e‑mail, and offline files. Files that aren't indexed include program files and system files—files that most people rarely need to search.
For more information on indexing, see the link below
Improve Windows searches using the index: frequently asked questions
(You may want to know ‘”How do I add or remove index locations? See this section in the link)
Thanks and Regards:
Ajay K
Microsoft Answers Support Engineer
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