I own 2 sticks of 2 gb kingston 1333mhz ram. They had been in there doing their job for two and a half years, and then I bought some g.skill ripjaw 2x4 1600 mhz ram. I tried replacing the kingston with the ripjaw, and that didn't work. now when I put it back to it's original state, it does not boot. The MEMOK light is on, but I don't really know what that is. I tried taking out the cpu and putting that back in because that worked for one case I saw on here. Thanks for helping.