Chronology of the PC

I have a new customer that was sold a “custom” built PC 8 months ago. The supplier used a cheap quality “everything on-board” motherboard and its AT format. The customer wants me to do some upgrade on the system, but I’ve told him It will need a newMB to do it. He claims that this system was sold to him as “new-state of the art”. I’m needing some kind of documentation that shows that AT boards are old and are no longer used in new systems by reputable suppliers. Can anyone suggest where I can get such info? I’ve been to Tom’s, and searched google, but no joy.