Finally, Sis handed me her gaming system for upgrading!

Mom's HP laptop now has an SSD instead of and HDD (but it is SATA!). Someday she will get an NVME in its place, as the system supports it.

Now, on Sis's build: the SteamGames HDD is now an SSD. As of this post, the original system drive is being mirrored to Mom's old HDD for final migration to the NVME on the new build.

Main reason is the build had a seamless transition from Windows 7 to Windows 10 by the use of two partitions on the old 1TB HDD. This time, the new build will not have this; the NVME is only 512GB. Windows 11 will not be installed on that system at this time, and only the Windows 10 partition will remain. Since the old system is BIOS/MBR, the setup will need to be converted to EFI/GPT for the new build.