A firewall is a blocking mechanism that helps to keep intruders out of a network (see Chapter 18 for more information about firewalls).
If you are connecting your Centrino laptop to a private network that is itself connected to the Internet, you are probably already protected by a firewall built in to the network hardware (the router) and do not need to enable a personal firewall.
However, if you are connecting to the Internet directly with your Centrino laptop, for example at a public hotspot, it is a wise precaution to enable the personal firewall software built in to Windows XP. (See Chapter 17, “Protecting Your Mobile Computer,” for more information.)
To enable the Windows XP personal firewall, open the Windows ...