I was installing Windows XP via VirtualBox using the "Windows XP Mode" official release from Microsoft, which gives you a
VirtualXP.vhd virtual hard disk file.
In the setup wizard, the default choice is:
Create a virtual hard disk now
I selected this and created a virtual hard disk. I thought I had already selected and used the downloaded file on the first page of the wizard.
But you'll get the
FATAL: No bootable medium found! System Halted. error when you run the VM.
Instead, in the situation where you are booting off a provided
.vhd rather than a
.iso, you should select:
Use an existing virtual hard disk file
and click the folder icon to select the
.vhd file you are trying to load.
Now your downloaded
.vhd is the "bootable medium", and VirtualBox won't be looking for a
.iso or CD drive to load.