Most firewalls will show you an alert when a program tries to send or receive data over the Internet, prompting you to block the program, unblock it, or defer your decision. If you don't see an alert, you'll have to unblock the program directly.
The procedure varies slightly from program to program, but it's largely the same. For instance, to unblock a program using the firewall in Norton Internet Security 2008, look for the Norton icon in the System Tray. The icon, which differs slightly fro...