Question: I bought a new laptop (Lenovo Thinkpad) which came with Windows 10 installed. I threw out the hard disk, replaced it with an SSD and installed Linux on it.

Now I put the old hard disk into an USB disk case and tried to boot, but Windows throws an error while booting (the USB disk was recognized properly and also the Windows partition was detected). The message says that the computer has to be restarted. It gives the following error code: `INACCESSIBLE_BOOT_DEVICE`

What do I have to do that I can boot the existing Windows 10 installation from USB? I would like to avoid swapping the SSD again, so solutions which keep the HD in the USB case are preferred.

Answer: 
Ah, `INACCESSIBLE BOOT DEVICE` seems to be a windows 10 favourite... 

The first possible solution is outlined below, with an extra twist in case you need it. It seems to work for most people, but as your circumstances are slightly different we will have to see:

1. At the blue screen where the error appears, click Advanced Options
2. Click Troubleshoot
3. Look for an "Advanced Startup" or "Startup Options" menu
4. A list of boot options is displayed
5. Click Restart
6. Upon restarting you'll be taken to the boot options you previously saw in #4
7. Boot into Safe Mode by pressing the appropriate key
8. Once you're back into your desktop in Safe Mode, reboot your PC and everything should be back to normal.

If this doesn't work, during the restart that you trigger in step 5 enter the BIOS and change your SATA mode controller to IDE from ACHI, or vice versa, and try safe mode again. If that doesn't work it's time to look at setting up a USB recovery drive to tackle the problem.

The issue often seems to arrive from a changed SATA controller mode, which usually is done when changing from an HDD to an SSD, but as I said thing might be a little different here, hope it helps.

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Additions based on comments:

I am aware that booting windows from a USB device is not natively supported, however I have myself achieved this in the past using a program which overcomes this limitation: [WintoUSB](http://www.easyuefi.com/wintousb/). I have only ever used this to create "new" installs of Windows, but it may be possible to leverage the same ability to boot an existing Windows installation.
Windows does not support boot from a USB disk.

Instead of booting directly from the external disk,
you could use VirtualBox to build a virtual machine that boots
from the external USB disk.

Here is one reference among the many that can be found :  

[Using a Physical Hard Drive with a VirtualBox VM](http://www.serverwatch.com/server-tutorials/using-a-physical-hard-drive-with-a-virtualbox-vm.html).