Windows 10: unknown account "S-1" in security/ file properties

Hi. an unknown account "S-1" which is unavailable on the computer except in "regedit" as shown in image is replacing registry files and even if remodifying the registry whereas immediately it takes back the registry even if removing/ denying type/ unselecting clicked choice, therefore such account comes back to win the settings leading other issues like Event ID: 2, 46, 69, 104, 417, 492, 1000, 8198, 10010, 10016 and preventing access Microsoft apps even if repairing/resetting setting of the apps.
how to resolve such issue, before its too late whereas i had to format windows last time but that unknown account reappeared.

:)

 

can i find out who is account unknown

I open the properties to a file under default user1 and then click

Security. i am concerned that an "account unknown" is listed.

here is part number

 

Remove account


I suggest you backup your personalized files first before removing the account.
To delete an account, follow these steps:

1. Press WIN + X keys and click Command Prompt (Admin) from the menu.
2. Type the following command and press Enter. Replace test with the name of your sister's account. Code:
   
   Code:

   net user test /del

 

Account Unknown has full Security permissions on my own User - huh?


Account Unknown(S-1-5-21-1345748419-2493160549-2943627078-1000)
has full permissions in the "Advanced Security Settings" for my own user account on my Win 10 Pro 64-bit PC.
What is it? Is this normal?

If I go to C:\Users\ , it lists four users:
[Myself]
Default
Default.migrated
Public.

If I right-click on [Myself] and hit Properties, then go to the security tab, it lists four "Group or user names:" with certain Permissions:
SYSTEM with full permissions - all items checked
Account Unknown(S-1-5-21-1345748419-2493160549-2943627078-1000) with the same full permissions - all items checked
[Myself] with the same full permissions - all items checked
Administrators with the same full permissions - all items checked

What is the Account Unknown(S-1-5-21-1345748419-2493160549-2943627078-1000), and how did it get there?

Two clues:
1) My PC is dual-booting Win 7 Pro 64-bit and this Win 10 Pro 64-bit. I'm in the Win 10
2) 15 minutes ago (and before checking this), I turned on Public file sharing so other PCs on my home network could see any documents I put in those Public folders or maybe vice versa. I do NOT have "Homegroup" turned on.

But wha' happening here?