The PC ID is generated by Mach4 based on several factors within your operating system. In order to protect our software, the details on that information is protected. Some (not all or even most) Windows updates affect those pieces of information used to create a PC ID, which is part of the reason our licensing policy is so generous. In the unlikely event you "run out" of usable licenses, open a ticket and let us know. I can honestly tell you no one has ever been denied a usable license because of excessive Windows updates.