Your memory is mismatched try using just the Corsair or just the Samsung they have different timings.
Corsair= 9-9-9-24 @666 MHz
Sammsung= 8-8-8-22 @ 609MHz
One or the other. Your MoBo only has one setting for speed and latancy, with this set at the highest 666Mhz your other RAM sticks are OC'd if you set it at 609 the others would be underclocked but may work. I'm pretty sure no MoBo auto function can't work with this mish mash of RAM sticks.
Could you briefly explain me how to do the following? What are the risks of keeping both rams? and underclocking would be better han removing the samsung?
To change your RAM speed and timings you have to enter Bios, reset your PC and when its starting up continuously tap delete until your BIOS screen comes up. In there there should be an advanced tab with memory frequency option, select your speed there, then select memory timings and enter the timing your choosing.
I can't be sure which will be faster you could try both ways if they will boot correctly and pass Memtest86, then benchmark each one with Sisoft Sandra(freeware) and see which one is better. I myself would get rid of the Samsung Sticks and just run with the Corsairs, simply because there is'nt alot of programs that need more than 6 GB.
Preferably I would sell all of them on eBay and buy a matching set.
This could be an issue with the motherboard not being compatible with RAM also as you didn't post any system specs.