Convert HDD to VHD

A Parallels virtual machine needs this conversion when it must run in Hyper-V, VirtualBox, or another platform that accepts VHD instead of Parallels' HDD format. The converted disk contains the guest system, but the destination VM may still need matching firmware, controller, and boot settings.

What the HDD format is

In virtualization, .hdd is the Parallels virtual hard disk format used by Parallels Desktop. On macOS, an HDD disk may appear as a package or directory containing a descriptor and one or more data files; on other systems it may appear as a single image. It contains the guest partitions, filesystems, operating system, and application data, rather than individual files that can be extracted like an archive.

Shut down the virtual machine before copying or converting its disk. A suspended or running VM can leave the image inconsistent. Parallels snapshots may store changed blocks separately, so the current snapshot state is not necessarily contained in the base HDD image.

What the VHD format is

.vhd is Microsoft's Virtual Hard Disk format, supported by Hyper-V, Virtual PC, VirtualBox, QEMU, and other virtualization products. VHD can be fixed, allocating its full virtual capacity when created, or dynamically expanding, initially using less host storage and growing as data is written.

Use VHD when the destination specifically requires the legacy format. For newer Hyper-V installations, VHDX is usually preferable because it supports larger disks and includes features intended to improve resilience; VHD remains useful for older hosts and cross-platform compatibility.

How to convert HDD to VHD

Using QEMU Disk Image Utility

qemu-img is the most practical general-purpose converter for this task. It can read the Parallels disk format and write a VHD without first creating a raw intermediate image. Install QEMU from the official QEMU project or a trusted operating-system package manager.

1. Power off the Parallels VM and back up the complete HDD package or directory, including its descriptor and data files.
2. In Parallels Desktop, merge or remove snapshots if the current snapshot state must be included. Do not convert only the base disk when newer data exists in a snapshot.
3. Inspect the image with qemu-img info "source.hdd". If the HDD is a package, use the package's descriptor or main image file, not an arbitrary split data segment.
4. Create a dynamically expanding VHD with qemu-img convert -p -f parallels -O vpc -o subformat=dynamic "source.hdd" "converted.vhd".
5. Create a fixed VHD instead with qemu-img convert -p -f parallels -O vpc -o subformat=fixed "source.hdd" "converted.vhd".
6. Verify the result with qemu-img info "converted.vhd". Check the reported format, virtual size, and backing-file information before attaching it.

On Windows, run the commands from the QEMU installation directory if qemu-img is not in PATH. Quote paths containing spaces. The destination needs enough free space for the output; a fixed VHD requires approximately its full virtual capacity.

Attach the converted disk

Create a new VM in the destination hypervisor and select Use an existing virtual hard disk, or attach converted.vhd after creating the VM. Match the source firmware and virtual controller type where possible, then test the converted disk on an isolated copy before deleting the HDD.

In Hyper-V, use New → Virtual Machine, choose Attach a virtual hard disk later, and add the VHD in the VM's hard-drive settings. Generation 1 uses BIOS-style booting; Generation 2 uses UEFI. A guest installed for BIOS may not boot in a Generation 2 VM, and a UEFI guest needs its EFI system partition preserved and UEFI enabled.

Compatibility and limitations

Conversion changes the virtual disk container, not the guest operating system or its drivers. Windows may require storage-controller drivers, activation, or boot repair after moving from Parallels to Hyper-V. Linux may require an initramfs rebuild when the virtual storage controller changes. Boot-repair tools should be used only on a copy of the converted disk.

Legacy VHD supports virtual disks up to approximately 2 TB; use VHDX for larger disks. Conversion does not transfer the Parallels VM definition, virtual hardware, network configuration, snapshots, or host-side encryption settings. A guest filesystem encrypted inside the disk remains encrypted and still requires its key or password. Unlock any Parallels-level protection and confirm that the source image is readable before converting it.

Online conversion is not suitable for most HDD images: files are large, may contain operating systems and credentials, and many services do not understand Parallels descriptors or snapshots. No general online service should be trusted with an entire VM disk; use local QEMU instead. Retain the original HDD until the new VM boots and its important files have been checked.