OK, I've done my A+, my partner in crime who runs our LAN is N+ certified and most of our regulars are IT Professionals in one capacity or another, and we can all confirm this, and will be adding video evidence at the next LAN.. The chances of this happening must be pretty slim, but anyway here goes... 2 of our regulars set-up their machines, and they were having wierd problems with their LAN connections. We were investigating both machines when we discovered the impossible, they had identical MAC Addresses. Now this is supposed to be impossible, infact it's part of the A+ training that states the first 24bits of the MAC address are for Manufacturer identification, and the second 24bits are for Card identification, to ensure there is no duplication. So what is the chance of this happening? And is it worth getting all the serial numbers from the boards and everything and mailing the manufacturer to let them know that: A: this has occurred B: that there may be a whole batch of motherboards out there with the same onboard NIC supplying the same MAC address to people. Anyone else ever experienced this?