Question Motherboard detects 2 Sticks of RAM but is only using one

[MattCodes]

My motherboard is detecting my 2 4GB DDR4 RAM sticks but is only using one of them

BIOS Image

In windows system information it displays 8.00GB (4.00GB useable)

Why is this? How can I fix this?

 

[hang-the-9]

Do you have a 32 bit version of Windows installed?