I have a 64-bit windows 10 desktop with 4GB (2x2GB) of memory. I purchased (2x2GB) more memory of the same brand/model/specs (literally just hit reorder from my original memory purchase) to bring the total up to 8GB but when I installed it, windows says 8GB is installed but only 4GB is usable. Furthermore, bios only recognized the 4GB. I removed the two new ones memory sticks that I purchased and went back to 4GB and it Windows now says 4GB installed and only 2GB usable. The bios also now recognizes only 2GB. I tried different slots on the MB but same issue. What gives!!!
Update: I reseated all the sticks and I'm now up to 8GB installed and 6GB usable.
Update: I reseated all the sticks and I'm now up to 8GB installed and 6GB usable.