Hi, I'm just double checking that I've been foolish here. I built my computer 2 years ago on a P8P67 Pro mobo and installed 2x2Gb of corsair CMX4GX3M2A1600C9. Without checking I ordered 2x2Gb more of the same RAM, the version no. was different but it had the same product number. The second set of RAM was not recognised. After checking the manual I see that this format wasn't supported. Is this correct? Using the Corsair Product checker they recommended CMX8GX3M2A2000C9 but this isn't in the QVL of ASUS? Any help is gratefully appreciated.