Can't use ram

[Soullreaver]

Hi, i had two rams hyperx 4gb 1866 mhz i bought third ram and when i insert it it doesnt show as usable i run ms config and it still wont use right amount of ram i have always missing those new 4 gigs

 

[jay32267]

Check your motherboard documentation regarding populating the RAM slots. Perhaps you need to add RAM in pairs.