Microsoft Toolkit, also know as EZ-Activator is a set of tools for any Windows computer that helps you manage, license, deploy and activate all KMS based Microsoft Office and Microsoft Windows products.
“KMS” (Key Management Service) is a technology used by Microsoft to activate software deployed in bulk (e.g., in a corporate environment). What Microsoft Toolkit does is to replace the installed key with a volume license key, create an emulated instance of a KMS server on your machine (or in previous iterations of the software, search for KMS servers online) and force the products to activate against this KMS server.
The latest version of this toolkit is 2.6.2 despite unofficial websites offering higher numbered versions (normally in an effort to entice visitors to download Viruses / Trojans).