After installing Symantec Protection Engine (SPE) with "SPE Based Authentication" on Windows, you seek to change to "Active Directory Based Authentication" without uninstalling / reinstalling.
This change can be made using the xmlmodifier.exe command in an elevated command prompt.
Note: As always, when working with the Protection Engine XML files, stop the Symantec Protection Engine Service. Please stop scanning within your connector before stopping Symantec Protection Engine Service due to potential negative impact to your scanning resource. See vendor documentation for best practices in disabling scanning.
Once you confirm the changes are within configuration.xml, you should be able to start the Symantec Protection Engine service and log into the console with your Active Directory credentials.
Note: Do not edit the Protection Engine XML files with anything but the XMLModifier
If you wish to go from Active Directory Authentication to SPE Authentication, be sure the password gets reset as per http://www.symantec.com/docs/TECH93561