Cannot start cmd.exe on Windows 10

Somehow I encountered the problem that I could not start the Windows Command Prompt (cmd.exe). The solution turns out is to remove a key from the registry. A number of posts points to the removal of HKCU\Software\Microsoft\Command Processor\AutoRun. A complexity comes from the factor that the user account is a standard user account; howeer, regedit needs to run as an administrator, which means the HKCU is the administrator, not the standard user.

To address this issue, we can perform the following steps

1. Figure out the user's sid:

   
       whoami /user
       

   The sid begins with S- that we can easily recognize from the output.
2. Open regedit, and browse to HKEY_USERS, to the user according to the user's sid, to Software, to Microsoft, to Command Processor, and then locate AutoRun, and remove it.

A StackOverflow post indicates several more keys to remove, but it is not necessary in my case, but it is good to document it, just in case in the future

reg delete "HKCU\Console" /f
reg delete "HKCU\Software\Microsoft\Command Processor" /v "AutoRun" /f
reg delete "HKLM\Software\Microsoft\Command Processor" /v "AutoRun" /f
reg delete "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File 
Execution Options\cmd.exe" /f