Frequently Asked Question
Extract .vmdk from OVA using 7zip.
Run from command line : VBoxManage.exe" clonemedium --format vhd infile.vmdk outfile.vhd
or for older versions of Virtualbox
VBoxManage.exe" clonehd --format vhd infile.vmdk outfile.vhd
2. qemu-img for windows
Great command line tool to convert from ova to vhd or vhdx
There is a free GUI program out there called CloneVDI that does not require any command line and has a few extra options. Did not used this one yet.