After a few more days of experiments, even though the solution hasn’t been found, there have been interesting and weird findings.
Here is what is happening and what I’ve seen so far.
DRIVER INSTALLATION:
Before the NVidia driver with added DEV_1D10&SUBSYS_09181028 strings is installed:
There is one MX150 entry in the Device Manager.
According to it, the OS sees the MX150 as “3D Video Controller” with question mark, with the ID “VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1”.
After the NVidia driver is installed, but before the OS is rebooted:
There is one MX150 entry in the Device Manager.
According to it, the OS sees the MX150 as “NVIDIA GeForce MX150” with yellow exclamation mark, with the ID “VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1”.
Device status: “You need to restart your computer before the changes you made to this device will take effect”.
After the NVidia driver is installed, and after the OS is rebooted:
On startup, the OS shows a small error window: “Problem Ejecting NVIDIA GeForce MX150”, “The ‘NVIDIA GeForce MX150’ device is not removable and cannot be ejected or unplugged”.
Pressing “OK”.
Opening the Device Manager, enabling “Show hidden devices”, and what I see:
There are TWO (!!!) entries related to the MX150!
Entry 1:
“NVIDIA GeForce MX150”, with the ID “VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1” - it’s dimmed / hidden / not connected.
Thus, the OS sees this device as disconnected.
This is the entry that supposed to be active and functional, for the MX150 to work and function - DEV_1D10&SUBSYS_09181028!
Entry 2:
“3D Video Controller” with question mark, with the ID “VEN_10DE&DEV_1D10&SUBSYS_00000000&REV_A1” - it’s active and connected.
SUBSYS_00000000 - WTF is this at all??
So, since the OS now sees the MX150 connected as DEV_1D10&SUBSYS_00000000 (while the actual device DEV_1D10&SUBSYS_09181028 as disconnected), and there’s no driver for the device DEV_1D10&SUBSYS_00000000, the “New Device Found” of Windows fails to find a driver for it, and it remains “3D Video Controller” with question mark in the Device Manager.
Conclusion:
After the driver installation and the OS restart,
The OS sees the actual device, DEV_1D10&SUBSYS_09181028, the device that supposed to be active and represent the functioning MX150 - as now-disconnected!
And instead, it starts seeing the MX150 as some mysterious device with the ID “DEV_1D10&SUBSYS_00000000”, with the corresponding second entry in the Device Manager.
I’ve done plenty of Windows 7 installations with all drivers on laptops (all of which were in Legacy/CSM mode), but I have never seen smth like this.
The word “weird” is a very soft word to describe what I’ve seen.
And given the fact that there is only one major difference between all previous laptops and the Dell 5401 in question - the use of UEFI class 3 without Legacy/CSM mode,
I continue thinking that the reason why all this is happening, is related to UEFI class 3 without Legacy/CSM mode.
Maybe this is the effect/outcome of the reaction of the UHD-630 driver or the MX150 driver on the exotic environment (which is Windows 7 used in UEFI class 3 without Legacy/CSM mode and with UefiSeven’s bootmgfw.efi).
Maybe something else caused by something related to being in UEFI class 3 without Legacy/CSM mode.
In any case I have no idea what’s going on.
And don’t know where else I need to dig.
EXPERIMENT:
So, I thought, why not adding another entry to the driver’s inf files, the entries with DEV_1D10&SUBSYS_00000000, get the driver for DEV_1D10&SUBSYS_00000000 installed and see what happens?
Maybe MX150 will function via the “device” this weird ID?
So, I made another driver modification, now with both “DEV_1D10&SUBSYS_09181028” and “DEV_1D10&SUBSYS_00000000” added entries, and repeated the experiment.
Before the NVidia driver is installed:
[same as before].
After the NVidia driver is installed, but before the OS is rebooted:
[same as before].
After the NVidia driver is installed, and after the OS is rebooted:
On startup, the OS starts the “New Device Found” thing.
With the new device being “DEV_1D10&SUBSYS_00000000”.
It finishes with a success: “NVIDIA GeForce MX150 installed”, “restart required”.
Opening the Device Manager, enabling “Show hidden devices”, and what I see there:
There are TWO entries related to the MX150.
Entry 1:
“NVIDIA GeForce MX150”, with the ID “VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1” - it’s dimmed / hidden / not connected.
Thus, the OS sees this device as disconnected.
This is the entry that supposed to be active and functional, for the MX150 to work and function - DEV_1D10&SUBSYS_09181028!
Entry 2:
“NVIDIA GeForce MX150” with yellow exclamation mark, with the ID “VEN_10DE&DEV_1D10&SUBSYS_00000000&REV_A1”.
Device status: “You need to restart your computer before the changes you made to this device will take effect”.
Restarting the OS.
While being very curious about what happens next.
After the NVidia driver is installed, and after the OS is rebooted for the 2nd time:
So, the OS loads.
The driver for the “device” DEV_1D10&SUBSYS_00000000 was installed successfully.
There is “NVIDIA Control Panel” both in the context menu and in tray!
Launching and minimizing various system monitor and process monitor software to track the newly installed device in the background.
Opening the Device Manager, enabling “Show hidden devices”, and what I see there:
There are TWO entries under “Display adapters” related to the MX150.
Entry 1:
“NVIDIA GeForce MX150”, with the ID “VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1” - it’s dimmed / hidden / not connected.
Thus, the OS sees this device as disconnected.
Again, this is the exact entry that supposed to be active and functional, for the MX150 to work and function properly.
Entry 2:
“NVIDIA GeForce MX150”, with the ID “VEN_10DE&DEV_1D10&SUBSYS_00000000&REV_A1”.
Device Manager shows it as a normal active device without any question/exclamation mark or errors.
Device status: “The device is working properly”.
Opening the NVIDIA Control Panel:
In “Adjust image settings with preview”, where the animated rotating NVidia’s 3D logo supposed to be, there is nothing.
Launching Rainmeter via context menu with manually chosen “High-performance graphics processor” (thus the MX150):
Process Hacker shows that the Intel’s iGPU is busy with Rainmeter, instead of dGPU.
Launching a test game via context menu with manually chosen “High-performance graphics processor” (thus the MX150):
The intro-video starts playing.
Pressing ESC.
The game closes.
Launching a test game via context menu with manually chosen “Integrated graphics processor” (thus the Intel UHD 630):
The intro-video starts playing.
Pressing ESC.
The game and its menu loads, saved game loads and I can continue playing.
Checking the system and process monitor software, and what I see:
The MX150’s load has never been higher than 0% and has been 0 at all times.
Conclusion, additional:
The DEV_1D10&SUBSYS_00000000 device that the OS sees after the driver installation - is a ghost device that is allright according to the OS, but in fact it doesn’t do anything and doesn’t work.
Despite the hacky driver installation for the device DEV_1D10&SUBSYS_00000000.
ADDITIONAL EXPERIMENT:
I uninstalled all GPU drivers (both dGPU and iGPU), and installed dGPU/MX150 drivers only.
After reboot, the MX150 is not used by the OS, which is kinda expected, since dGPU is usually dependent on iGPU.
Opening the Device Manager, enabling “Show hidden devices”, and what I see there:
There is only one entry representing MX150:
“NVIDIA GeForce MX150”, with its normal ID (“VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1”).
Device Manager shows it as a normal active device without any question/exclamation mark or errors.
Device status: “The device is working properly”.
Now, with the installed dGPU and non-installed iGPU, I decided to try to install the iGPU driver. (So, the reverse installation order - iGPU after dGPU).
Installed, rebooted the OS, and ended up with the same SUBSYS_00000000-crap as in the previous experiment:
On startup, the OS starts the “New Device Found” thing.
With the new device being “DEV_1D10&SUBSYS_00000000”.
It finishes with a success: “NVIDIA GeForce MX150 installed”, “restart required”.
Opening the Device Manager, enabling “Show hidden devices”, and what I see there:
There are TWO entries related to the MX150.
Entry 1:
“NVIDIA GeForce MX150”, with the ID “VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1” - it’s dimmed / hidden / not connected.
Thus, the OS sees this device as disconnected.
This is the entry that supposed to be active and functional, for the MX150 to work and function - DEV_1D10&SUBSYS_09181028!
Entry 2:
“NVIDIA GeForce MX150” with yellow exclamation mark, with the ID “VEN_10DE&DEV_1D10&SUBSYS_00000000&REV_A1”.
Device status: “You need to restart your computer before the changes you made to this device will take effect”.
Restarting the OS.
While being very curious about what happens next.
After the NVidia driver is installed, and after the OS is rebooted for the 2nd time:
So, the OS loads.
The driver for the “device” DEV_1D10&SUBSYS_00000000 was installed successfully.
There is “NVIDIA Control Panel” both in the context menu and in tray!
Launching and minimizing various system monitor and process monitor software to track the newly installed device in the background.
Opening the Device Manager, enabling “Show hidden devices”, and what I see there:
There are TWO entries under “Display adapters” related to the MX150.
Entry 1:
“NVIDIA GeForce MX150”, with the ID “VEN_10DE&DEV_1D10&SUBSYS_09181028&REV_A1” - it’s dimmed / hidden / not connected.
Thus, the OS sees this device as disconnected.
Again, this is the exact entry that supposed to be active and functional, for the MX150 to work and function properly.
Entry 2:
“NVIDIA GeForce MX150”, with the ID “VEN_10DE&DEV_1D10&SUBSYS_00000000&REV_A1”.
Device Manager shows it as a normal active device without any question/exclamation mark or errors.
Device status: “The device is working properly”.
Does anyone have any idea what the hell is going on? 
