I did not have any luck with Starwind V2V Converter. Even though it mentioned free I ran into problems due to limited features.

Here are two truly free methods that I have tested and used:

  • VirtualBox (Windows and Linux)
  • qemu-img (Windows)

VirtualBox

Download the software from the official site

Open Command Prompt as Admin and run this command:

cd C:\Program Files\Oracle\VirtualBox

Next run the following command with the correct paths to the vhdx file and where you want to store the copy

VBoxManage clonehd --format vmdk C:\temp\PLEX.vhdx ะก:\temp\PLEX.vmdk

The Linux command is very similar so if you are using Linux you should be able to figure it out but email me if you need help.

Qemu-img

Download qemu-img from the official site

Open a Command Prompt as Admin to the location of the program and you can run this command to view the disk info:

qemu-img.exe info c:\temp\PLEX.vhd

Here is an example of how to convert a vhdx file:

qemu-img.exe convert -p c:\temp\PLEX.vhdx -O vmdk c:\temp\PLEX.vmdk

One thing I want to note is I did receive the following error on ESXi 6.5

Error: File system specific implementation of LookupAndOpen[file] failed.

I never figured out the issue however the file did work ok for a while on ESXi 6.0. I say a while because the disk then had problems because the file was over 2TB

however after the upgrade I could not get the VM to run anymore and had to rebuild my PLEX server so create good backups if your vmdk file is large

I tried the following from the server with no luck

clone VM folder:

cp /PLEX.vmdk /temp/PLEX-fixed.vmdk

Use vmkfstools:

vmkfstools -i PLEX.vmdk PLEX-fixed.vmdk

References:

https://www.nakivo.com/blog/how-to-convert-vhd-to-vmdk-a-step-by-step-guide/
https://kb.vmware.com/s/article/82057
https://communities.vmware.com/t5/ESXi-Discussions/Check-VMDK-for-Corruption/td-p/2282728
https://kb.vmware.com/s/article/82673