StarWind V2V Converter

StarWind Converter is a free downloadable V2V conversion tool for virtual machines.  You can use it to convert VMDK to VHD files and VHD to VMDK.  It is a sector by sector copy operation from one format to the other. It does not modify the source image and will leave it so you can continue to use it.

http://www.starwindsoftware.com/converter