How to Use Windows XP: Activating and Configuring Windows Firewall
1. Click the Start button.

2. The Start Menu will appear.

2. Select the Control Panel icon.
3. The Control Panel window will appear.

4. Select the Security Center icon.
5. The Security Center window will appear.

6. Make sure that next to Firewall there is a green dot and it says ON.
7. If it says OFF next to Firewall, select the Recommendations button.

8. The Recommendation window will appear.

9. Select the Enable now button.
10. A Security Center window will appear

11. Select the Close button.
12. Windows Firewall has been enabled and is protecting your computer.