I bought two hp z400 and two z420 motherboards from three different sellers ALL were DOA!! I had the CPUs they came with and I bought my own CPU I bought dual core quad core and hexacore CPUs I swapped out the ram the cooling system the power supply and even the chassis and hard drive NOTHING works! I ended up buying a generic socket 2011 motherboard for my hexacore and a dell xps 435t motherboard for my hexacore. Has anyone else had a mass of DOAs with these boards?? Am I doing something obviously wrong that is not obvious to me somehow?