Convert VHD Free is a simple tool which makes it easier to convert drives into Microsoft's VHD virtual drive format.
The program has two main functions.
It can convert VMware VMDK virtual files into the VHD equivalent. Just choose your source VMDK file, enter a VHD destination, click Convert and leave the program to do its work.
And you can also convert a physical drive into a VHD format, which can be useful if you'd like to run your installed applications within a virtual machine. Again, just choose the source drive, a destination, click Convert, and the program will run a sector-by-sector copy for you.
Convert VHD Free would be more useful with VirtualBox support, or if it could also convert from VHD to VMDK. It's free, though, and if you only need conversions to VHD then the program makes that very straightforward.