The crucial website says that the Ballistix Tactical 4GB DDR3-1600 UDIMM LP is not compatible with the Intel DQ67SW. I found this odd because it is compatible with Ballistix Tactical 8GB DDR3-1600 UDIMM LP. The only difference is the memory size between these kits as far as I can tell. They have the same voltage, CAS latency and speed. Therfore I have no reason to believe there is any incompatibility despite what the crucial compatibility checker says. If anyone could provide further insight that would be much appreciated.