Technitium MAC Address Changer is a tool which provides useful information on your network adapters, and enables you to change their MAC addresses to something else.
Why bother? A utility like this can help to improve your privacy when accessing public networks on a laptop, for example (if your MAC address is always changing then you'll appear to be different systems). It can be useful for testing network security, and may have some troubleshooting applications, too.
At a minimum, you can use Technitium MAC Address Changer to find out more about a particular network adapter. Just choose it from the list and you'll see its name, hardware ID, current MAC address and who that belongs to (the card manufacturer, in other words), connection speed, and even a graph showing current network traffic.
And in a click or two you can now also change an adapter's IP address, gateway, DNS server and more.
If you want to change an adapter's MAC address, though, there's the option to create one randomly, enter a particular address of your own, or even choose one from the program's extensive list. The new address can be just for this session, or be made persistent (so it'll survive a reboot), and if you've finished testing then you're able to restore the original address with a click.
There are a few complications involved here which means this process won't always be successful. It worked for us, though, and there is an option you can apply if you have problems (click "Why" next to "Use '02' as first octet of MAC address), so if you need to engage in this kind of advanced network tweakery then Technitium MAC Address Changer is a good place to start.