Yes, it boots to Windows. I have not powered up the machine without the original HP SDD. I simply installed the M.2 drive and closed the machine back up. This HP is a pain to open and it involves taking off the back. It's double difficult because one of the hinges is broken and I have to reattach the back with the laptop open. I loved the old Toshibas that had a panel on the bottom that you can remove and access the hard drive bay.
Anyway, looking at the boot options, is it as simple as changing to the Kingston (M.2) drive in this menu?