Windows 10: Strange "Unknown" User Account on Security Tab

I happened to look at the Security tab of file properties and noticed a strange "Unknown" user account.


The SID isn't listed in the registry under HKEY_Users and doesn't appear in Control Panel User Accounts.


Should I delete this account? How can I figure out what it is?







:)

 

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

Brink - thanks for suggestion.
But I'm not sure about this at all.
By the way, if I open a cmd and do the wmic (or wimc?) command to show all the accounts, this unknown one does not appear!
What's the worst that could happen if I delete this unknown account from the security tab?

 

Strange Windows 10 User Account issue.

Unfortunately I had done those steps numerous reboots, it just, reappears for no good reason. The base account isn't even a Microsoft account, it's a local account.

I haven't quite tried the built in administrator account on W10, but so far in my experience on my own computer, the built in account seemed to have absolutely no more control than I did on my own.

It's just strange, I go in, it warns me twice about deleting the account, then it's gone. Reboot, and it's back?

EDIT: Just to specify, both command line and Netplwiz both say only HIS account exists on the computer, it doesn't list this rogue account. This is what I meant in my first post about the fact that even Windows doesn't seem to believe it exists, HALF the time. *Frown

 

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

and if its listed in the registry like in my case then what? *Redface