Not sure but the frequency on CPUz is the speed you're ram is running, maybe you're os is reading the actual devider setting that you're running you're memory from as I see you're bios says it only supports upto 1066mhz, maybe that's what windows is reading in error, but you're ram is running at the speed on the memory tab from CPUz and it also talllies up with the freq set in you're bios