HP notebook stuck in "System reset..." restart boot loop after installing Linux Mint

[DuHundDuOIDA]

Stuck in an endless loop?

I've installed Linux Mint via USB on an HP ProBook and after the first installation process I had to restart the computer so the OS can be configured to completion.

Here's what happened after restart:

HP Logo appears first, then the message "Reset system..." and the loop never ends. It just restarts all the time...

I was testing out all boot modes (Legacy, UEFI w/ and w/o CSM) to troubleshoot, if it wasn't working, because of the wrong boot environment (even secure boot option was always deactivated), but it didn't matter what i did, it never worked.

The boot order was always SSD, USB hard drive, OS boot manager, PXE....
So my SSD was the source where my Linux Mint got installed, but it won't boot.

(In legacy mode it always started a PXE boot, even though I had my SSD as the first and PXE as the 4th or 5th boot option???)

What I did was:

I was spamming the "Esc"-button to get to the hp startup menu, went under BIOS Setup (F10), further jumped to Advanced Settings and entered the Boot Options menu. (Not mandatory, but I deactivated all boot options I didn't need as PXE, USB, ...just to get it "out of the way") and created a new custom boot option, by activating "Custom boot" > set a tick at "Add boot" and filled in "EFI\ubuntu\grubx64.efi" as the path. I made sure the Custom boot was the first boot option (before my SSD and the other options...) and SAVED my changes, before exiting out of the BIOS menu and restarting the notebook.

And it worked.

If you're not sure what the correct path is, where the bootloader for your OS (in my case Linux) is located in, you can manually navigate to it (via EFI File Navigator in the Startup Menu) by restarting your computer/notebook, spam "Esc", when in the Startup Menu, go to F9 Boot Device Options, navigate through "Boot from EFI File">"Select File System" (it appears as something like ",Acpi(PNP0A03,0/PCi(1F|2)/Sata(Port 0).....")>EFI>ubuntu (or your OS name)>hopefully you can see all bootloaders (I can choose from 3 and they all end with "...x64.efi"). Remember the path or write it down and write it into the custom boot segment (as explained above).