I have 2 sticks of 1600mhz DDR3 RAM installed however when using dual channel ram slots (1-3, 2-4) windows only recognises 12GB and says only 7.98 is usable. CPU-Z says I have 16GB installed and when I put the ram sticks next to eachother (slots 1-2) I'm back to 16GB so don't think its a hardware error. Any ideas of what I could do?