virtualbox.org

How to install the VMs I know.
However how to install Virtualbox on a Live CD that's my the question.

You're not going to install VirtualBox on a LiveDVD, neither you're going to touch your host.

You're going to boot the Windows VM while having the LiveDVD in the VM's optical drive, following the instructions from scottgus1.

1. Select your VM.
2. Click on the Optical Drive in the Details pane (right-hand side).
3. Choose the SystemRescueCD ISO that you've hopefully downloaded.
4. Start the VM, it's going to start from the DVD, the SystemRescueCD in this case.
5. Wait until it completely boots and issue the command:

   • nproc

Once you're done, eject the SystemRescueCD from the Optical Drive. Your VM is going to be unharmed...

Have got it by my own.
I cleaned the directories of the VMs. Only the virtual disks remained.
I uninstalled Virtualbox, and then I reinstalled it.
Then I created new VMs with the same virtual disks as before from the command line.
Now everything runs as expected.

I think the reason was:
First I addionally installed phpvirtualbox für my mouse pushing Windows coworker.
This time I didn't and never will do again.
Thanks again to all who tried to help.

HAKAK

HAKAK wrote:First I addionally installed phpvirtualbox für my mouse pushing Windows coworker.

That's why it's important to reveal all the details of a problem... Have a chat with them, see if they can pinpoint the source of the problem: phpVirtualBox support.

Marking as [WorksForMe].