If you plan to do the P2V conversion operation , you can use the following tools

Method A: VMware vCenter Converter Standalone

Use a converter software product by VMware which is free to download using the link below:

http://downloads.vmware.com/d/  

Method B: StarWind V2V Converter

If your .VHD is not in any of the above cases (i.e. backup image) then you can use StarWind software tool to do this conversion. I like this product as it is free to use, simple and does the job. You can download it from this link:

http://www.starwindsoftware.com/download-starwind-converter

Method C: Convert .VHD to .VMDK with WinImage

http://www.technorati.com/tag/WinImage