Windows Firewall is a firewall service that is turned on by default in Microsoft Windows XP Service Pack 2. To determine if Windows Firewall is enabled, follow these steps:

1. Click on the Start menu.
2. Click Run.
3. Type in "firewall.cpl" (without quotes) and then click OK.
4. Under the General tab, click "On (recommended)" if it is not already selected.
5. Click on OK.

Windows Firewall is now turned on.

-- OR --

1. Click on the Start menu.
2. Click on Control Panel (if Control Panel option is not displayed, click on Settings, then click on Control Panel).
3. Double-click on Windows Firewall (if Windows Firewall option is not displayed, click on Switch to Classic View in the left panel, then double-click Windows Firewall).
4. Under the General tab, click "On (recommended)" if it is not already selected.
5. Click on OK.

Windows Firewall is now enabled.