When doing this you actually wouldn't be changing the MAC address, only changing what the things connecting to your comp. Think it is. Which would be why your MAC address wouldn't change permanently because it is stored on the NIC itself. Im pretty sure on a ROM chip(because it makes sense.) To improve the tutorial you may want to start out by explaining what a MAC address is so people would know why they wanted to change it, it's use in security, stuff along that lines.