Ok on a reboot, when u see the bios load screen, press Del a few times until it loads up the bios.
Once inside the bios, choose MB Intelligent Tweaker (M.I.T.), and press enter.
On the next screen choose Advanced Memory Settings, and press enter.
Highlight Extreme Memory Profile and hit enter to see if there are any XMP profiles on your memory, if there is it will say profile 1/profile 2 and give u certain speeds depending on the profiles. Not all memory uses XMP, so don't worry if u can't see any of that. So if it allows this choose a profile that is close to the rated speed of 2000mhz, but not over it, and hit enter, then press F10 and leave the bios and reboot.
If you can't use XMP then follow this.
Highlight system memory multiplier and hit enter, now you will get to choose from one of the multipliers, take not of the Memory Frequency number below this, it will change each time u select a new multiplier.
So check what each multiplier gives you, and decide which one you want, it will be like 1066/1333 and so on, depending on multi.
So set that to the highest you can thats closest to the memory's rated speed without going over it.
Once you have done that, hit esc to go back to the MIT page.
At this point we want to go into the Advanced Voltage settings.
You want to arrow down to Dram Voltage and change it to 1.65v, and hit enter, then press F10 and leave the bios. And let it reboot.
Hope this makes sense.