Ok. Let me know how it goes.
Additional note:
This is what's shown if I double-click "Administrator" in the lusrmgr.msc applet.
This browser is no longer supported.
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.
The built-in Administrator account is missing from my system.
Microsoft Windows Version 10.0.26100.4652 Microsoft Corporation. All rights reserved.
C:\Windows\System32>net user
User accounts for JIM-DESKTOP
DefaultAccount Guest Jim
WDAGUtilityAccount WsiAccount
The command completed successfully.
C:\Windows\System32>net user administrator /active:yes
The user name could not be found.
More help is available by typing NET HELPMSG 2221.
C:\Windows\System32>
How do I get it back?
Ok. Let me know how it goes.
Additional note:
This is what's shown if I double-click "Administrator" in the lusrmgr.msc applet.
Glad that helped.
You can check the status of the account by running the following from Command Prompt after booting into Windows:
net user administrator
wmic useraccount get name, sid
Also, follow up with a full system scan using ESET Online Scanner or Kaspersky Virus Removal Tool.
You can try this.
Create a System Restore Point.
Download add_admin.reg and save it to the C:\ root.
Boot into WinRE and run:
reg load HKLM\SAM2 H:\Windows\System32\Config\SAM
regedit.exe
Import add_admin REG file using the File → Import option.
Close Regedit.
Run:
reg query HKLM\SAM2\SAM\Domains\Account\Users\000001F4 >H:\sam_dump.txt
reg unload HKLM\SAM2
Post the output.
Boot into WinRE Command Prompt and run this command:
bcdedit | find "osdevice"
Note the OS partition's drive-letter. Suppose it's D:\
Run:
copy D:\Windows\System32\Config\SAM D:\SAM.bak
reg load HKLM\SAM2 D:\Windows\System32\Config\SAM
reg query HKLM\SAM2\SAM\Domains\Account\Users\Names
reg query HKLM\SAM2\SAM\Domains\Account\Users
reg unload HKLM\SAM2
Post the output.
Please run the following command and post the output.
wmic useraccount get name, sid