The most common cause of this problem is a corrupted or improperly removed previous version of Symantec AntiVirus or Norton AntiVirus. To fix the problem, uninstall Symantec AntiVirus. Before you install Symantec AntiVirus again, follow the manual uninstallation instructions for the latest version that you installed and for the previously installed version.
For help with this, read the document
Manual uninstallation documents for Symantec Client Security products.