Windows won't boot with 8gb ever since Radeon 6950 was installed

Oh, also do you know if the DIMM 1 slot isnt working, would it affect the DIMM 3 slot? because I have 3 installed, it even says "installed memory: 6GB" but only showing 4GB as total memory.

You can install a single stick in Slot DDR3_3 without a stick in DDR3_1.

I'm having trouble keeping track of what you are doing. I think you have four 2GB sticks of RAM. Do you have just 3?

"it even says "installed memory: 6GB" but only showing 4GB as total memory" is confusing. What says this? What shows that? The BIOS? Windows?