I opened an Explorer window, right-clicked on a folder, and clicked the Security tab. The issue is this: I see a user whose name is shown as S-1-5-80-... I would like to know which user this is because I see no such name when I go to Control Panel->Users. Please suggest something for me to try - thanks.
This can happen if a user account had been deleted.
User accounts in the form shown are how Windows identifies accounts internally. The name is for humans who have trouble remembering long numbers. When the security tab is displayed Windows will attempt to lookup the number in the accounts database and display the associated name. If the user account has been deleted this will of course fail. If the file or folder had specific rights assigned to such an account Windows will display the account number as the name no longer exists.
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