I am a bit baffled about what I just tried to do. I have a machine running Windows 8.1. I have VirtualBox installed. Let's call this MACHINE-A. On MACHINE-A I have a VirtualBox Guest that runs off of an External USB 3 drive (EXT-DRIVE) with an external VMDK virtual hard disk. This is a Windows 7 Guest. It runs great.
Now I have a new machine running Windows 10 that also has VirtualBox installed. Let's call that MACHINE-B. I hooked up the EXT-DRIVE to MACHINE-B. I used Disk Configuration to map the EXT-DRIVE to use the same drive letter that EXT-DRIVE uses on MACHINE-A. (Drive W:)
Then, on MACHINE-B, I setup a VirtualBox Guest using almost the EXACT same settings of the virtual machine on MACHINE-A using the same Virtual Hard drive (VMDK) that is on the EXT-DRIVE.
However, when I attempt to start the new guest on MACHINE-B I am getting a Windows Boot error. It says something about Hardware changing, lists the fix options, and then says "The boot selection failed because a required device is inaccessible".
I was surprised at this. I thought the new guest on MACHINE-B would work out the partitions automatically. But it is like it isn't finding the System Reserved partition.
Is there a way to get this to work?