hoop-jumping is a program designed to allow you to quickly alter your MAC address on Windows, usually in order to coax a uncooperative network to allow you internet access. It works by directly altering the MAC address values in the registry.
You first select the network driver that you would like to change the MAC address for, then you insert the MAC address that you would like to use. If a device driver does not have a MAC address (usually some form of virtual driver), it warns you that it might make the device unstable.