You are not able to remove Symantec Scan Engine from Add/remove programs.
Symantec recommends uninstalling Symantec AntiVirus Scan Engine 5.x through Add/Remove programs or the Start menu.
To Remove Symantec Antivirus Scan Engine manually on Windows based computer.
To edit the registry and remove the Symantec AntiVirus Scan Engine keys
To remove Symantec AntiVirus Scan Engine files and folders
NOTE: In case these folders cannot be removed (because they are still in use), reboot the machine and try again
In some cases it might be necessary to follow a few extra steps to ensure a clean uninstall.
Remove Symantec Scan Engine remnants from the Installer folder:
From C:\Windows\Installer, remove all files and subfolders that refer to Symantec Scan Engine.
If the folder Installer is not visible, do the following:
WARNING : It is recommended to keep the Installer folder hidden!
Clear the Temp folders from Symantec Scan Engine-related files
In case a reinstall is considered, clear the Temp folders from Symantec Scan Engine traces. These temp folders can typically be found in
Reboot the computer.