Begin by determining which version of Windows XP you are currently running:

1. Either from the desktop or from the Start Menu, right-click on My Computer.
2. Click on Properties.
3. Under the General tab, it will state either "Service Pack 3," "Service Pack 2," "Service Pack 1," or neither will be displayed.
(If neither is displayed, then you are currently running an earlier version of Windows XP.)
4. Proceed to the appropriate section below.

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The following instructions apply to Microsoft Windows XP Service Packs 2 and 3.

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.
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The following instructions apply to Windows XP Service Pack 1 and earlier versions of Windows XP.

In Windows XP Service Pack 1 and earlier versions of Windows XP, the firewall service is called Internet Connection Firewall. To determine if Internet Connection Firewall is enabled, follow these steps:

1. Click on the Start menu.
2. Click Run.
3. Type in "control.exe netconnections" (without quotes) and then click OK.
4. Right-click the network connection on which you connect to the Internet and click on Properties.
5. Under the Advanced tab, click the box next to the option "Protect my computer and network by limiting or preventing access to this computer from the Internet" if it does not already have a check mark in the box.
6. Click on OK.

Internet Connection Firewall is now turned on.