not usable ram

I know this question is all over the internet but I cannot find a solution. My computer in system settings reports 16.0 GB of ram yet only 15.8 GB is usable. I know this is a very small amount that is not usable but I would still like to have all my ram usable since I paid for it. In BIOS it...

Hello I buyed a new Mobo yesterday. I checked it and its all fine, no damage on Mobo. I installed the CPU and I had no display, so I removed and reput cpu a lot of times(also changed thermal paste 2-3 times). After so many times. when i turned on my pc again, I heard a buzzing noise from psu. I...