With reference to the article on irongeeks site.

http://www.irongeek.com/i.php?page=security/changemac

I would like to add that there is one more way that i know of in windows xp to change the MAC address and i have done it successfully. I wouls like him to add it to his tutorial.

Here are the steps
1. Open the network connections from the taskbar
2. Select the connection and open properties
3. Diable the connection
4. Alongside the Network Card(connect using) is the Configure option
5. In that select the Advanced tab
6. Move to the network address property
7. Check the Value radio button and type the new address. Note it has auto limit to type 12 characters and not more
8. save and reenable the connection.

This would change the MAC address.