Install Win 10 to m.2 SSD in 640 G1

[sejarzo]

I recently purchased a used 640 G1 in which the seller had removed the 2.5" SSD with Windows 10 and installed a new one but installed Linux on it, as an MBR disk. I was able to install and activate Win 10 Pro on that SSD, used MBR2GPT to convert it from MBR to GPT, then change the boot mode to UEFI in setup and everything ran just fine. As it's only a 120GB and can't hold my multimedia files, I wanted to install a spare 2.5" HDD for those but boot from the m.2 slot. I purchased a 120GB m.2 2242 and installed it in the m.2 slot, booted up, and it was immediately visible in Disk Management, where I designated it as a GPT disk.

I then attempted to clone the Win 10 installation to it using easeUS Todo, which has worked well for me in the past.  Even though the new m.2 is the same capacity as the 2.5 SSD, easeUS insisted that it couldn't clone it because the m.2 drive was too small.

So I decided that as I didn't have many apps installed, I would simply remove the original 2.5" SSD and do a fresh install of Win 10 on the m.2 drive. I reset the boot mode to UEFI with CSM and it booted up into the installation off a freshly prepared Win 10 installation USB. The installation appeared to run absolutely normally to the point where it normally reboots to complete the installation (connection to the wireless network, etc.) but it refused to do so. I can't recall the exact wording but I got a screen that implied there was no bootable media in the notebook and it would shutdown.

I have seen conflicting info in other threads about the proper steps to install Win 10 on an m.2 SSD in the 640. I'd be very grateful if someone could lay out the precise steps to get the BIOS to recognize the USB install stick all the way through to getting the notebook to boot from the m.2 slot to complete the installation, then reliably boot from the m.2 slot.

My apologies if I have simply been unable to find an existing thread with the info, but I am still recovering from eye surgery and may have missed it. Thanks very much!

[sejarzo]

I may have found an answer from an older thread.

Can someone confirm that there is a limitation in the 640 G1 BIOS that does not allow a drive in the m.2 slot to be used as a default boot drive?

I assumed Windows would not start an installation on a drive if that were the case, but it seems that perhaps I guessed wrongly.

[sejarzo]

Grasping at straws here...

At the bottom of the BIOS' list of boot devices/locations there's an option shown as "Customized Boot." The Technical White Paper at http://h10032.www1.hp.com/ctg/Manual/c04685655 states the function of that option as:

"Allows boot from a custom boot path; loads the boot loader from the path defined in Define Customized Boot Option (see below)"

The only info in the section below is:

"Specifies path for the customized boot option
Note: Only boots from this path if Customized Boot is enabled"

Is there any way to define that path to point to the proper file on the m.2 drive? As I noted previously, I could see the m.2 drive within Windows 10 after it was booted from the 2.5" SSD after I ensured that the option for m.2 SSD was enabled in the BIOS. To me, that means the machine should be able to see the m.2 drive on power up, but that Technical White Paper gives no guidance/example for the syntax of the path to a drive in that slot before the drive is recognized in Windows .

Thanks in advance for reading this and any suggestions.