Hi, I do not have Mac OS X running as guest, so I can not test this and therefore must ask someone who has Mac OS X running as guest. Which serial number of the Mac do you see inside the virtual machine, when opening the System Profiler of the Guest? Do you see the serial number of the host the VM is running on inside the VM, or do you see the serial number of the host the VM has been created on, or do you see a completely different value there? Is the serial number of the Mac a piece of hardware emulated by the virtual machine and therefore independent from the host it is running on, or is the serial number of the Mac a piece of hardware not emulated but simply passed thru like the CPU? Do virtual machines break uniqueness of the serial number of the Mac by cloning it?