Bizarrely small available memory when running 32-bit Windows 7 on ZBook G3

[BorisShpungin]

First, some background:

I recently purchased a ZBook 15 G3 with Windows 10 Professional 64-bit pre-installed.  The laptop has two SSDs; Windows 10 was pre-installed on one of them -- let's call it the primary drive, while the second SSD I'll call the secondary drive.

At work, we have an application that must be run on Windows 7 Professional SP1 32-bit OS.  (Note in particular: 32-bit!)

I have managed to install the 32-bit Windows 7 onto a special partition I made on the secondary drive, by changing its default GPT setup to MBR using the diskpart tool (otherwise, Windows 7 installer refuses to install on a GPT drive), and having previously updated the installer to incorporate USB and NVME drivers in a manner similar to what HP advises to do for 64-bit Windows 7 installations here:

http://h20566.www2.hp.com/hpsc/doc/public/display?sp4ts.oid=8693763&docLocale=en_US&docId=emr_na-c05...

In order to boot into it, I disable the UEFI Boot Order in the UEFI/'BIOS' settings, and go with secure boot disabled and legacy support enabled (I haven't yet figured out how to boot into it via UEFI -- if that's at all possible -- but that's not my major problem right now.)

In that installation, I've downloaded/installed most of the 32-bit drivers for all the devices I care about, and disabled the rest.  I've run all Windows Updates on that Windows 7 install as well, and everything is completely up to date.  I've also updated the BIOS on the ZBook to the latest available as of this writing: 01.09 Rev.A, dated 4 Jul 2016.

Now, the issue:

For the most part it works and looks just fine.  However, despite the laptop having 32 GB of RAM installed (in case it matters, I have it configured with 2x16 GB sticks of DDR4 ECC 2133 DRAM and a Xeon E3-1545M CPU, as well as NVIDIA Quadro M2000M graphics card)...

Anyway, despite having 32 GB of RAM in the machine, the Resouce Monitor reports that out of the 32,768 MB of "Installed" memory, 32,015 MB are "Hardware Reserved" with only 753 MB "Total" available as "Physical Memory".   (The "System and Security\System" panel in the Control Panel similarly reports that of the 32.0 GB of "installed memory (RAM)", only 754 MB are "usable".)  Out of that quantity, the OS and default applications/services normally take up roughly 600 MB, leaving a whopping 150 MB or so for user-launched applications!  Needless to say, the impact on performance is rather abysmal with all the resulting disk thrashing and page faulting.

So...  I would totally understand if I only had somewhere in the range between 4 and 2 GB of RAM available (since a 32-bit OS can't address more than 4 GB, and there have to be allowances made for resources reserved by various hardware.)  That's the situation on another one of my laptops (a Sager custom build, with 16 GB of DDR4 RAM on it) that also has a similar Windows 10 Pro 64-bit + Windows 7 Pro SP1 32-bit dual-OS setup.  That would be fine.

But having only 753 (or 754?) MB of RAM available in total, to be shared across the OS and user applications, is just absolutely ludicrous.  Now I've tried everything I could think of.  I tried removing one of the memory sticks (reducing the system total to 16 GB) -- with absolutely no effect.  I tried all sorts of bootloader options via bcdedit, including disabling PAE, 'increaseuserva', 'nolowmem', and 'truncatememory'.  Absolutely no effect.  I'm just about at my wit's end with this.  The most frustrating thing isn't even that I can't find a solution, but that I don't even understand what's causing this problem in the first place.

Is this due to some kind of a bug with the current ZBook G3 firmware/BIOS?

Please somebody, help!