Many times I have been able to physically move the old windows 10 hard drive from old computer to new computer and it worked fine. However, with some of the new computers---especially the Dell 3471 it doesn't recognize that the hard drive is a bootable windows 10 drive. It recognizes it fine in BIOS but it fails to allow booting from it. I can stick the same hard drive in an older computer and it will boot from it just fine. I am wondering if it something to do with the secure boot options is stopping it from booting in these new computers? I tried turning off secure boot and playing with the BIOS settings and have been able to get it to boot from a usb flash drive but never from the old hard drive. I tried this with two different Dell 3471 computers with two different hard drives from working computers and they refuse to allow booting from the drive(s). Any ideas????