I installed the memory in DIMM 3 & 4, ran memory diagnostic, got errors for DIMM 3 no matter which stick was installed. Put one stick in DIMM 4, ran diagnostic, passed green on all tests. I am now running the machine with one stick in DIMM 4.
What would this indicate? Both DIMM 1 & 3 evidently have issues? What is common element on motherboard whose failure would impact DIMM 1 and 3 but not 2 & 4?
Sorry, Dell does not accept trades, for a replacement motherboard, try calling Dell Spare Parts HERE.
Note: Dell replacement parts are marked 'Refurbished' and have only a 90 day warranty.