MAC addresses were designed to be fixed numbers that cannot be changed. However, there are several valid reasons to want to change your MAC address
Changing a MAC Address To Work With Your ISP
Most Internet subscriptions allow the customer only a single IP address. The Internet Service Provider (ISP) may assign one static (fixed) IP address […]

The method used to find a MAC address depends on the type of network device involved. All popular network operating systems contain utility programs that allow one to find (and sometimes change) MAC address settings.
Find a MAC Address in Windows
In Windows 95, Windows 98 and Windows ME, the winipcfg utility displays the computer’s MAC address. […]