If you’re running Windows XP Service Pack 2 (SP2) the new Windows Firewall is turned on by default.
Because a firewall restricts communication between your computer and the Internet, you might need to adjust settings for some programs that prefer an open connection. These adjustments are called “exceptions.”
Windows Firewall now has three settings: On, On with no exceptions, and Off.
To enable Windows Firewall in Windows XP, follow these steps:
1. Click Start, click Run, type Firewall.cpl, and then click OK.
2. On the General tab, click On (recommended).
3. Click OK.
If the General tab or the On (recommended) option is unavailable, the system may have a policy against running the firewall. Contact the system administrator for more information about how to enable the firewall. In addition, the system may already be running a third-party firewall (Zone Alarm or Norton Internet Security, for example). Contact the system administrator for help in determining whether a firewall is already running on the system.