When a user account is perpetually or repeatedly locked out, we need to identify the source. If the source identified is the user's computer, we need to reset credentials on the computer.
1. Clear out local credentials
Open a command prompt and run the following command.
rundll32 keymgr.dll,KRShowKeyMgr
This will open up the "Stored User Names and Passwords" dialog.
Check each credential, if it references the user account in question, remove it.
2. Clear out system credentials
This takes a bit more work to access. We have to run the same command as the local system account.
The easiest way to do so is to use PsExec from SysInternals PsTools.
With PsTools installed you can now run the following command from an administrator command prompt.
psexec -i -s -d rundll32.exe keymgr.dll,KRShowKeyMgr
The -i tells it to interact with the desktop session.
The -s tells it to run as local system.
The -d tells it not to wait for the process to finish.
This opens the "Stored User Names and Passwords" dialog for the local system account, which may contain additional references to the user account.
Check each credential, if it references the user account in question, remove it.