Hello,
In your Case, the best option is to uninstall SEP as ofcourse, you cannot upgrade as you don't have license for the same.
You wouldn't receive any notification, as probably you may have not registered for the same.
Installing Either Norton Version or Purchasing Symantec Endpoint Protection License may help you get the upgraded version.
The issue in your machine is not Corruption of SEP. However, there were some bugs in version SEP 11.0.2000 which were not fixed and the same in your case was not fixed since last 2 years.
Incase if you have a latest version, here are the steps below to upgrade which is recommended.
Since you are carrying Older version 11.0.2000
We recommend you to upgrade the Symantec Endpoint Protection Manager and all clients to Latest version.
Since you are carrying old version, there would be 2 upgrades you will have to go through. Please check the steps below:
1) From Symantec Endpoint Protection 11.0.2000 to Symantec Endpoint Protection 11.0.6005 (RU6a)
http://www.symantec.com/business/support/index?page=content&id=TECH131653&locale=en_US
2) From Symantec Endpoint Protection 11.0.6005 (RU6a) to Symantec Endpoint Protection 11.0.6300 (RU6 MP3)
http://www.symantec.com/business/support/index?page=content&id=TECH155655
Reason:---> check the Release Notes below:
Release notes for Symantec Endpoint Protection 11.0.x and Symantec Network Access Control 11.0.x