When you attempt to start the Windows 7 firewall service you receive the following error
Windows could not start the Windows Firewall on Local Computer. For more information, review the system event log. If this is a non-Microsoft service, contact the service vendor, and refer to service-specific error code 5.
If you look in the System Event Log, you will see event 7024 from the Service Control Manager
The Windows Firewall service terminated with service-specific error Access is denied..