Checking for Windows XP Firewall
To see if you're running Windows Firewall:
- Click on the Windows Start button, and select Control Panel. The Control panel window will appear.
- Click on the Security Center link. The Security Center will appear.
- If the Firewall header says ON, you are running Windows Firewall.
Configuring Windows XP Firewall
If you're running Windows Firewall and having connection problems in Firefox:
- Click on the Windows Start button, and select Control Panel. The Control panel window will appear.
- Click on the Security Center link. The Security Center will appear.
- If the Firewall header says ON, you are running Windows Firewall.
- Ensure that Don't allow exceptions is not selected.
- Click to select the Exceptions tab.
- Find Mozilla Firefox (or firefox.exe) in the list of programs. If it is there, click to select it. If not, skip the next step.
- With Mozilla Firefox selected, click the button. Confirm that you want to delete the entry.
- Click the button.
- In the Add a Program window, click the button.
- Navigate to the Firefox program directory (e.g. C:\Program Files\Mozilla Firefox\) and double-click on firefox.exe.
- Click the button to close the Add a Program window.
- Click the Firewall Settings window. button to close the Windows
Source:- http://support.mozilla.com/en-US/kb/Configuring+Windows+Firewall