Same old 8GB (3.96 USABLE) RAM USAGE

[Joao Ferreira]

GOOD AFTERNOON EVERYONE, I'VE BUILD MY OWN DESKTOP http://ca.pcpartpicker.com/p/28WT6 BUT CAN'T USE ALL AVALABLE MEMORY.
RAM'S ARE ON POSITION 1 AND 4 ON MOTHERBOARD, IF I CHANGED THEM TO OTHER POSITIONS OR IT WON'T EVEN START OR ACT REALLY WEIRD.
CAN SOMEONE HELP ME FIX THIS PROBLEM?
THANK YOU VERY MUCH IN ADVANCE FOR ANY HELP FROM YOU GUYS