FATAL: No bootable medium found! System halted: how to fix it in VirtualBox

What the error means

Oracle’s manual says VirtualBox uses BIOS firmware for virtual machines by default. The message appears when none of the devices in the boot order holds anything bootable. It isn’t a VirtualBox crash and nothing on your PC is damaged; the VM simply has nothing to load. That’s why the fix is almost always a settings change rather than a reinstall.

Find your situation

When you see it	Likely reason	Go to
First start of a brand-new VM	No ISO in the virtual DVD drive	Fix 1
ISO is attached but the VM still halts	Boot order, or a UEFI-only ISO on a BIOS VM	Fix 2 and Fix 3
Installing Windows 11	EFI isn’t enabled	Fix 3
After the install finished, or after removing the ISO	The OS didn’t install to the virtual disk, or the disk isn’t attached	Fix 4
After importing, cloning or moving a VM	Disk detached, or the firmware doesn’t match how the disk was installed	Fix 4 and Fix 3

Fix 1: Attach the installation ISO

1. Shut the VM down completely (Machine > ACPI Shutdown, or close the window and choose Power off the machine).
2. Select the VM in VirtualBox Manager and open Settings > Storage.
3. Under the controller (usually IDE or SATA), select the optical drive marked Empty. If there’s no optical drive, select the controller and use the add button to add an Optical Drive.
4. In the Attributes pane, click the disc icon next to the optical drive and choose your ISO file from your PC.
5. Select OK and start the VM. It should now boot into the installer.

If the VM is already running, you can also insert the ISO from the VM window’s Devices menu, which the manual says can change removable media while the guest is running. Restart the VM afterwards so it boots from the disc. If the installer still doesn’t start, download the ISO again: a broken or incomplete download can’t boot.

Creating a new VM in VirtualBox 7 attaches the ISO for you and, if the image supports it, runs an unattended install. Ticking Skip Unattended Installation still mounts the ISO, according to Oracle, but leaves the install to you.

Fix 2: Check the boot order

Open Settings > System > Motherboard and look at Boot Order. Make sure Optical and Hard Disk are ticked. For a new install, put Optical above Hard Disk, because a blank virtual disk listed first gives the same error. Once Windows is installed you can move Hard Disk back to the top.

Fix 3: Turn on EFI for Windows 11 and UEFI media

A BIOS-mode VM can’t start from media that only supports UEFI, and Oracle’s manual notes that most modern Windows and macOS releases require UEFI. On the same Settings > System > Motherboard tab, tick Enable EFI (older versions label it Enable EFI (special OSes only)). For Windows 11, VirtualBox 7 can also provide a virtual TPM and Secure Boot on that tab; Windows 11’s setup checks for both.

This works in reverse too. A disk that was installed in BIOS mode won’t boot once EFI is switched on, and a disk installed with EFI won’t boot without it. If a VM that used to work starts showing the error after you changed this box, set it back. Our explainer on Secure Boot state covers what the UEFI and Secure Boot settings mean.

Fix 4: Make sure the virtual hard disk is attached

If the error appears after the installation was supposed to have finished, check Settings > Storage again. You should see a hard disk file (.vdi, .vmdk or .vhd) under a controller. If there’s none, add the existing disk with the add button and choose Hard Disk, then select the file from the VM’s folder. Don’t create a new disk, which would be empty.

If the disk is attached but the VM still halts once the ISO is removed, the installation most likely didn’t finish or was written somewhere else. Put the ISO back, boot from it and check whether the installer sees an existing Windows installation on the disk. If it doesn’t, run the installation again. For a disk copied from another VM, match that VM’s EFI setting as described in Fix 3.

If the VM won’t start at all and you get a different message, see failed to open a session for the virtual machine or Not in a Hypervisor Partition.

Doing it with VBoxManage

The same fixes work from the command line, which helps when you manage several VMs. Open Command Prompt in the VirtualBox install folder (normally C:\Program Files\Oracle\VirtualBox) with the VM powered off. Replace the VM name, controller name and ISO path with your own; the controller name must match what Settings > Storage shows.

VBoxManage storageattach "Win11" --storagectl "SATA" --port 1 --device 0 --type dvddrive --medium "C:\ISO\Win11.iso"
VBoxManage modifyvm "Win11" --boot1 dvd --boot2 disk
VBoxManage modifyvm "Win11" --firmware efi

The first line puts the ISO in a DVD drive on port 1 of the SATA controller, the second sets the boot order, and the third switches the VM to EFI. Use --firmware bios to go back. If Windows itself later reports a boot configuration problem during setup, see Windows could not update the computer’s boot configuration.

Related guides

• Failed to open a session for the virtual machine: VirtualBox fixes
• Not in a Hypervisor Partition (HVP=0): how to fix the VirtualBox error on Windows
• Secure Boot state: how to check it and what On, Off and Unsupported mean
• Windows could not update the computer’s boot configuration: how to fix it

Official sources

• Oracle VirtualBox User Guide: Configuring virtual machines (firmware, boot order, storage)
• Oracle VirtualBox User Guide: Creating a virtual machine and unattended installation
• Oracle VirtualBox User Guide: VBoxManage reference