A free utility from Star Wind utility which converts virtual disk files VHD/VHDX/VMDK by essentially cloning the virtual machine into the new format. This was handy for me today, needed to convert Win 2012 VHD for use in VMware workstation and then back again on my laptop.
The utility allows the selection of Thin/Thick destination formats, which is handy. Certainly worth a look at if you need a quick way to go between virtual disk formats.
Click here to download