I've used a Mac Scanner and the computer that doesnt stop at 12 PM, is an iMac.
Its powered off most of the time, I guess only teachers use it, so I dont think there'll be a clash sorta thing.
I've tried changing it in the Network Address option of the adapter in the Device Manager, but when I restarted it and ran ipconfig /all, the MAC was still the same.
And yes, the device runs on Win-8