In an elevated Command Prompt (that is, Run
cmd.exe or Powershell as Administrator), run the following command:
sc delete "Locker Service For User A"
This will delete the existing Windows Service called "Locker Service For User A."
If you see this error:
[SC] OpenSCManager FAILED 5:
Access is denied.
This means you are not elevated to Administrator Command Prompt.
More information on Windows Services can be found here: https://technet.microsoft.com/en-us/library/cc755249(v=ws.11).aspx
More information on creating a PK Protect Locker in the PEM Administrator can be found here: Creating a Smartcrypt Locker