virtualbox.org

I'm running Vbox 5.0.16 with the host being Ubuntu 15.10. This is a new install. (I had previously tried the Ubuntu VB version and it didn't work at all, so I'm already ahead of the game).

I DLed the AMD-64 version file from virtualbox.org, installed it with apt-get and then installed the extension pack.

I have an old VM Windows 7 host that contains vital programs and data that I need to be able to access, so I can't just install a new Win7 host. The structure I'm using is /mnt/sdb/VirtualBox VMs/Win7-32/Win7-32.vbox. Note this file was from a 4.x VB install.

So I boot up. I get warnings about shared directories having changed and auto capture keyboard. I was able to adjust the settings so I'm not getting those alerts anymore. I set up the old 4.x host file with Machine > Add and navigate to the Win7-32.vbox file. Then I hit 'start.'

I get the Oracle splash screen, then the message "FATAL: Could not read from the boot medium! System halted."

What boot medium? Doesn't the Win7-32.vbox and .vdi files contain the entire Windows OS in some sort of virtual drive? I'm very confused here. HELP!!

Found a solution at https://www.youtube.com/watch?v=S8j1Fo2KRZM

The posted "solution" is to find the original bootable CD or virtual hard drive the virtual machine was using before it was moved to the new host.

I have an old VM Windows 7 host that contains vital programs and data that I need to be able to access, so I can't just install a new Win7 host. The structure I'm using is /mnt/sdb/VirtualBox VMs/Win7-32/Win7-32.vbox

Based on the discussion of a vbox file named Win7, I believe the way you are using the term "host" is wrong. The "host" is the physical PC you're running Virtualbox on. Your physical PC seems to be running Ubuntu, so you have a Linux Ubuntu host. The Win7 files define a "guest", which is the term for a virtual machine running under Virtualbox. Ubuntu host, Windows 7 guest.

There are other files that can make up a guest besides the .vbox and the .vdi, especially if one has been using snapshots. The correct way to move a version 4 guest is here: Moving a VM

I had drafted a reply similar to yours, but the OP's second post arrived before I hit submit!

I suspect that he had something, perhaps the guest additions iso, assigned to the optical drive in the guest, and it tried to boot from that.