Your MAC address is a physical address stored in your network card, by the manufacturer. Usually, this address doesn't change. You can retrieve your address, to use it in filtration, such as a firewall or router. Follow these steps, for Windows XP.

1. Click on the Start button and locate the Control Panel icon.
   
   
   or
   
   
2. In the Control Panel folder, locate Network Connections.
   OR>
3. Right click on the adapter you want get the MAC address for and click on Status.
   
4. In the Status window, click on the Support tab (Step1), then Details (Step2).
   
5. The Physical Address is the MAC address for the adapter.