Re-register MSI by:
Start run -> msiexec /unregserver ->click OK
then
Start run -> msiexec /regserver ->click OK
Reference: http://www.symantec.com/connect/forums/i-cant-uninstall-or-remove-feature-endpoint-client-my-manager-server
Incase upon Registering the MSI , Receive Error: "Process marked for deletion"
1) Install Windows Installer 4.5 Redistributable on the server and restarted the server.
http://www.microsoft.com/downloads/details.aspx?FamilyID=5a58b56f-60b6-4412-95b9-54d056d6f9f4&displaylang=en
2) Re-register MSI by:
Start run -> msiexec /unregserver ->click OK
then
Start run -> msiexec /regserver ->click OK
3) Uninstall Liveupdate and Check if the Windows Installer service is in Stopped mode and type is Manual.
4) Re - run the Setup.exe file for Symantec Endpoint Protection Manager.