Different ram modules

[Knife_1]

So i recently wanted to oc my cpu, and every time i tried to load into windows it would crash(blue screen)
I tried every combination of speed/cpu voltage/ram voltage but failed
My theory is that the ram is the problem, because the RAM modules are different in terms of capacity and frequency, and i wanted your opinion on this.
The specs of the pc
CPU :Intel core 2 duo e6750
RAM: 7Gb DDR2 :2x2GB unbranded ram at 556mh/z
1x2 gb samsung at 800 mh/z
1x1 crucial 800 mh/z
Motherboard:Asus P5B with the lates BIOS
GPU:Nvidia GTX 750ti
And a 750W PSU
+2 TB of storage(if it matters)

 

[RememberThe5th]

The problem is when you try to overclock the 556MHz ram probably cannot go any higher, as most unbranded generic are allready overclocked if you bought from China.
Try without unbranded/generic.