Each game requires a globally unique identifier (GUID) that it uses to identify itself on the communications medium. These GUIDs, sometimes called UUIDs, can be generated on any computer that has a network card and a copy of Uuidgen.exe, provided as part of the Microsoft Win32® SDK. You create a GUID once while developing the game, and use that GUID throughout the life of the product. There is no need to register this number with Microsoft.