Problem with 64GB of RAM in the form of 4 x 16GB modules showing up as only 32GB (31.xGB useable) was finally resolved when I followed this seemingly strange procedure on youtube: https://www.youtube.com/watch?v=oFK2eB51_Ss It basically changed a single setting in the registry; then check that someone has not told "msconfig.exe" to use a limited amount of the available RAM (a legitimate process used by software and hardware testers and developers); then swapped the DIMM order. I had the same problem with running all these 3 OS's: Windows 7, Windows Server 2016 and Windows 10 Pro, so I think this is mainly associated with the DIMM order or imperfect seating causing some issue. Perhaps it is to do with two slightly different batches of DIMM's. I initially ordered 2 x 16GB (32GB) installed them and then added another 2 a few weeks later from another source, without considering the pairing in appropriate corresponding slots. Motherboard: GA-AX370-Gaming K7 (re