After a rather arduous and convoluted series of problems that left me without a desktop for ~80 days, I've finally got the thing up and running, having replaced the power supply, motherboard, graphics card and CPU. Now, however, I'm experiencing the 'hardware reserved RAM' issue. Perhaps this is the exhaustion talking, but looking at the question that tends to get pointed to when this kind of topic gets locked as a duplicate hasn't helped.
I have 16 GB of RAM installed in an MSi 970A-G46, which is spec'd for up to 32 GB of RAM. The BIOS recognizes that I have 16 GB installed, and the resource monitor also shows the whole 16 GB, only it shows 8 GB as hardware reserved. I've seen suggestions that it's an OS issue, but the particular installation of Windows 7 (64-bit) which I'm running on my boot drive is the same as the one that could actually access the 16 GB in my previous motherboard (MSi 870A-G54).
I've updated my BIOS using the MSi Live Update tool and restarted the machine with no effect, and I cannot seem to locate any 'Memory Remapping' option as I've seen mentioned. I've physically swapped the RAM between the slots to no effect. I've unchecked the Maximum Memory box in the msconfig Boot tab's advanced options, also to no effect.
These are my system's basic specifications
OS: Windows 7 Home Premium (64-Bit)
Motherboard: MSi 970A-G46
CPU: AMD FX-8150
Graphics Card: XFX Radeon HD 6870
Boot Drive: OCZ Agility 3
Storage Drive: Samsung Spinpoint F3 ST1000DM005/HD103SJ 1TB
PSU: Thermaltake TR-2 TR600 600W ATX12V v2.3