DavidR
2
The avast firewall is designed to work with the windows firewall, so it doesn’t actually disable it. So there would appear to be something else going on on your system, e.g. why the service can’t be started “Windows cannot start the Windows Firewall service.”
Unfortunately I don’t use Vista so I can’t really say what to look for and I long ago gave up on the windows firewall, preferring to have a more user friendly one, which is more configurable and provides outbound firewall protection.
Lots of search hits on the windows vista error http://uk.search.yahoo.com/search?p=Vista+"Windows+cannot+start+the+Windows+Firewall+service", this one from MS seems a good place to start. http://answers.microsoft.com/en-us/windows/forum/windows_vista-performance/cannot-start-windows-firewall-for-vista/8d3ab846-d5a9-4df1-bb1e-a6f4842abc63