Ok, memtest shows all my ram is functioning fine. I can install any ram in any of the first 3 banks and windows boots up and runs fine. Installing into the 4th and final bank locks windows up at the starting up screen before the checkered flag appears. Bios recognizes the memory. I'm using the boards fail safe defaults. The memory is G-skill F3-12800CL9D-4GBNQ DS 1600mhz DDR3, system auto clocked it down to 1333. Using a Intel I5-750 with HD 5770 graphics card. SATA HD and IDE DVD. I found I couldn't install windows 7 on this new machine without removing that last stick as well kept locking up at different points. Could it be a bad memory slot in the board or is there something i'm missing.