You should remember, that Microsoft uses software license keys to activate each instance if its software. There are two types of activation mechanisms, one where each instance of the software is activated directly with Microsoft (or through an activation proxy) independently of each other using a single MAK (Multiple Activation Key). The other activation method deploys an activation server within the organisation to allow individual software instances to activate internally using KMS (Key Management Service) without communicating directly with Microsoft. Upon activation, the key is checked online with Microsoft to determine its validity, and keys used by unauthorised users are subsequently withdrawn and further activation requests using the compromised key are rejected. The key itself can be a string of characters entered into the installer or the software itself which by some method of computational comparison verifies the entered key and subsequently continues the installation process or the execution of the software. The key can also be a hardware dongle that physically connects with the computer making the key less vulnerable to copying. Generally speaking, circumventing copy protection schemes based on either software license keys or hardware dongles through reverse engineering of the verification code is not complicated unless rigorous code protection mechanisms are put in place to obfuscate the copy protection itself. Bear in mind that all protection systems can (and will, given enough time and resources) be broken.