Microsoft says that product activation does not scan a user's hard drive or register the make and model of the PC with the company. Instead, a random installation ID is generated using unnamed parts of the hardware configuration, and the Product ID, and that number is registered along with the Product ID at Microsoft. Users concerned about changing their system's configuration have nothing to fear: Microsoft understands that people upgrade components in their systems and their product activation scheme takes this into account. If a user completely recreates a system from scratch, say replacing the motherboard and other main components simultaneously, they will need to call Microsoft to activate the product when it is re-registered. This process will make it impossible to reinstall the OS on the old system.