I have Intel DP55KG motherboard, and i bought 8gb of ram too. I bought two memory kits and i plugged #1 kit to blue coloured memory slots and the #2 kit balck coloured. When i start the computer, The BIOS post screen shows me numbers 21 and mobo beeps three times. When i unplug two stics of memory, computer strts normally. So i unblugged one stick at blue sockets and one at black sockets.