PC has a Gigabyte GA970 DS3 mother board with 16 GB of Patriot DDR3 ram 4 x 4GB. I upgraded from 8 to 16 several years ago. Initially everything worked as expected. Recently, I found that when I look at PC properties I only see 14 GB with 12GB usable. In Bios I see 12270MB. Recently it straightened itself out for a few days and all was well, but yesterday I found the system locked up and unresponsive, and when I look, I am back to 14GB with 12GB usable. If I run CPUz everything looks fine. I ran memory diagnostics with no problems found. It does impact my work on this machine, a DAW for music production. Processor is AMD FX 8300. I did recently install new drivers for the graphics card, Nvidia GEforce and wonder if that's part of the problem? The fact it's intermittent makes it more difficult. nothing I've tried points to the problem, so I'm asking for suggestions of what to try next?