Even easier, boot into the BIOS, reset the CMOS to its defaults and then Exit, saving changes. Reboot into the BIOS. Now, with reference to your motherboard manual (Chapter 2.5 Ai Tweaker menu), make the following changes. Do not change any other settings.
1) Ai Overclock Tuner > set to D.O.C.P
2) DRAM O.C. Profile > set to DDR3-1600MHz
Exit, saving changes. Reboot into the BIOS and check to see that the memory is correctly reporting the selected speed. Now reboot into Windows and post back with an image showing the Memory tab of CPU-Z.