FIXED. I put back my old HD with Windows 7 ( was in storage for few month in case I want to revers back ) and I still have the same problem, I said WTF I have a slot defective, I go in the bios under GPU.DIMM Post, and guess what the 4th slot was NA,, I try the GPU in all other slot and it was working, SO I inspect the slot 4 and one of the tab was bent and lay down at the bottom of the slot. SO I use a needle and my bino and I redress it and put back in place. So now I'M back in business. Honestly I don't see how this tab get bent like that, the upper part seem to be broke, so I guess it's a manufacture problem. Anyway i'm allergic to RMA so I keep it like this, if one day this tab broke definitively, I will use this board with a single GPU.