To run a firewall different than the windows firewall, (for example Zone Alarm, products from Symantec or Kerio) the windows firewall should be deactivated. In order to do so, go to the used network connection under “Control panel/Network connections” and select “Properties/Advanced/Internet connection firewall”. By unchecking the option “protect my computer and network by limiting or preventing access to this computer from the internet” the firewall is deactivated.