how i fix this error /critical error: cannotfind entityclassregistry table in scripts / how i fix plz help me i wanna play far cry but i can't

Almost sounds like you need to reinstall so you can correctly enter the secret serial number but I don't think Farcry has a serial number for security protection. Maybe your registry is damaged or that your Farcry was never able to install to the registry. Run Yahoo anti adaware. Try the farcry updates.