Added ram, computer won't boot

Hello

I added 4gb ram into my computer which already had 4gb in two seperate dimm slots. Now my computer struggles to boot (fans spin then turns off) multiple times before booting with no post. The CPU Led light is on and there are no beeps.

I have cleared CMOS and tried using only one dimm slot for ram still no post. I have taken everything apart and put it back together with no success. I know I shouldn't have added extra ram which is different mhz to my current ram in another dimm slot but I'm baffled as to why it won't boot still.

My specs are:

Asus Maximus Formula III
I7-860
Nvidia 560ti
2x2gb ram
1tb HD
500gb HD
128 ssd

Thanks, any help would be much appreciated.