How To Change Computer MAC address in Windows XP

MAC address.
MAC is an acronym that stand for Media Access Control (aka Hardware Address). MAC is an address given to a computer's Ethernet NIC, Gigabit Ethernet NIC or wireless 802.11a/b/g/n WiFi or HiperLAN adapter right from the place of manufacture that means each/any computer that have the means of network connection has a unique MAC address which is quite different from any computer that have network card attached to them just like in a network, any computer connected has its own IP address.

From http://compnetworking.about.com

The MAC address is a unique value associated with a network adapter. MAC addresses are also known as hardware addresses or physical addresses. They uniquely identify an adapter on a LAN.  

As you can see the MAC address also play it's role in computer networking, whenever you access/connect to any network, the network router will record your entrance by taking your device MAC address and your computer IP address. In a situation where your computer is been restricted from entering to a network or taking part in other network activities, the only thing you can do to hide your ass is by hiding your MAC address and IP in order to bypass MAC address filtering on firewall or router this trick is called MAC address spoofing; although MAC address are imprinted to the network card and can not be changed. However, operating system can spoof as if there is different MAC address for the network interface card using trick below.

—Click Start >> Control panel >>In the Control Panel click Network Connections > right-click on the active network connection then click on Properties

—Click Configuration from General tab then Click on Advanced tab.
—In the Property section, select and highlight Network Address or Locally Administered Address.
—To the right, “Not Present” radio button is by default selected as value. Change the value by clicking on radio button for Value:, and then type in a new MAC address to assign to the NIC.
This is an example of MAC address  00-0D-56-F5-F9-03 that's it
When changing the MAC address don't put the dash (-).
Click OK when your done.

To confirm your change. type ipconfig /all in the Command line (Start> Run type CMD then press Enter)
If your changes is successful, you'll have to reboot your system for it to take proper effect.
To restore the default MAC address go back to the properties section and select the radio button  “Not Present” then reboot the system.
These settings is only applicable to Windows OS