Key Management Service
There is an unofficial KMS server emulator that will activate Windows or Office even if the software was not licensed or paid for, and regardless of whether or not there are 25 or more computers on the network. There is also a program that will send KMS requests to a legitimate KMS server, in order to fool the server into thinking that there are 25 or more computers on the network. Microsoft considers both of these exploits to be a violation of the Terms and Conditions.