RAM Problem..

[av180]

Hello, I have a custom comuter that wasn't working properly.. It was choppy when it shouldn't be, and it ramdomly shuts down.. So we got a diagnostic from a computer repair store (tigerdirect) and they told us our hardrive was slow (green) which caused the choppyness but i havent tested yet.. They also told us to take out 1 stick of ram (2gb) to have 6gb. Or use up all 6 slots with, 12gb. So, i come home install windows download a game overnight. Wake up this morning to see my computers off. I turned it on and it shuts off. Then, i turned it on and it shuts off again, and again, and again. So i have a feeling its something to do with the extra 4gb of ram to make 12gb from my previous 8gb which made the computer shut off randomly. So my question is, is there any settings i have to change for me to use up all six slots? or anything i need to do so i can run 12gb of ram smoothly no shut downs! Now ill give u my computer specs

MOTHERBOARD: EVGA X58 SLI LE, 3 Way SLI, PCI Express 2.0, Intel Core i7
MEMORY (RAM): 12GB(shuts off =[ ) 4 2x2gb Corsair XMS3 DDR3 RAM
PROCESSOR: Intel i7 920 @ 2.67ghz (Going to overclock to 3.2ghz after this problem is resolved.)
VIDEO CARD: EVGA GeForce GTX 560ti 1GB GDDR5
WINDOWS: 7 64-bit
POWER SUPPLY: 750W


Soooo, i need help.. any answers while i wait and read up on my motherboard manual to check things out ...

 

[av180]

Okay, so i read up on the manual and took out the 3 RAM sticks to have 6.. now gonna see if it shuts down.