Changing boot device

[Topher406]

Just unpackaged this computer. I want to pull the SSD from my old PC and install it in this new PC, and boot from the swapped SSD. I went into BIOS, and changed the boot order....It still boots from the preinstalled SSD. I removed that SSD entirely, and BIOS says I don't have a boot device. The drive I installed HAS an OS on it (Windows 10).  So why won't this new PC boot from that drive?

[itsmyname]

@Topher406 --  I went into BIOS, and changed the boot order

That should have done it. 

How old is the old disk-drive? 

Was Windows installed on a computer that did not support "secure boot", but the new computer requires that the disk-drive be marked as "secure-boot" ?  If the old disk-drive is not properly "tagged", then the motherboard will not try to boot from the old disk-drive.

Instead:

1. remove the SSD from the old computer
2. boot the new computer from the new disk-drive
3. download & install & run the free MACRIUM REFLECT software, to "clone" from the new disk-drive onto the SSD
4. shutdown
5. disconnect the new disk-drive
6. start-up, and immediately enter BIOS SETUP
7. configure the new SSD to be the primary "bootable" device
8. exit from BIOS SETUP

Does the computer now boot correctly from the SSD?

[Topher406]

I don't want to clone the new factory installed drive onto the old drive. The old drive has programs that are difficult to reinstall on a new drive. That's why I wanted to just ditch the factory drive, and install the one from my previous PC. Is there a way to make the old drive secure-boot compatible? Is there a way to disable secure-boot? 

[Topher406]

I also disabled secure boot and TPM in BIOS. I cleared all stored boot keys. It still boots to the factory installed drive. 

[itsmyname]

@Topher406 --  It still boots to the factory installed drive

Enter BIOS Setup.  

There should be a "boot" option in the menu.

Either that menu will display a list of devices, for you to re-order, to put the "new" disk to the top of the list, or the menu will display a list of "groups" -- the "disk-drive" group, the "removable media" group, and so on.

In the latter case, select the "disk-drive" group, and re-order the members of that group to put the "new" disk to the top of the group.

[VH2000]

If your old PC runs in BIOS Mode and your new in UEFI, it will not work.
If your old drive has more than 3 Partitions you will not be able to convert it to GPT.
If your old PC has an AMD-CPU and your new has an Intel-CPU it will not work
If ...
There are many things to do

[itsmyname]

@VH2000 -- If your old PC has an AMD-CPU and your new has an Intel-CPU it will not work

I disagree. 

I have noticed that Windows 10 will "adapt" itself quite liberally, to "vastly-changed" hardware, such as a switch from AMD processors to Intel processors.  In the past, earlier versions of Windows were not so "accommodating". 

Of course, there are Microsoft Licensing issues. An "activated" license to run Windows 10 is tied to a specific computer.  So, it seems to be a violation of the license to move the disk-drive (now containing an activated product-key) to connect it to a different motherboard/network-adapter/CPU. By "different", I do not mean replacing a failed motherboard by an identical (except for internal serial-number) motherboard.