OK so I switched the mobos around and I get the same DRAM orange LED issue, which leads me to believe I must have done something to the CPU when switching the cooler around maybe. I am going to try and update the BIOS on the motherboards tomorrow and see if that makes any difference, but bearing in mind I was running Windows fine for 2-3 days without any issue I cannot see it being the BIOS. Worth a shot though. I guess I will then need to test the CPU somehow, probably by sending it back to the retailer. Ugh.