Hello,
As everyone highlighted above, Symantec Endpoint Protection 12.1.671 does not support Windows 2012 and Windows 8.
However, Symantec Endpoint Protection 12.1.RU2 and above does support Windows 2012 and Windows 8.
About Windows 8 and Symantec Endpoint Protection 12.1
http://www.symantec.com/docs/TECH174348
In your case, you may like to Uninstall SEP 12.1.671, for which you can follow this Article::
Methods for uninstalling Symantec Endpoint Protection
http://www.symantec.com/docs/TECH184988
Hope that helps!!