The file is located in Program Files/Oracle/VirtualBox/VBoxManage.exe
and is used as a command-line interface with VirtualBox.
I'm using it to convert the .vdi image to a .vdmk (for VMware).
http://scottlinux.com/2011/06/24/convert-vdi-to-vmdk-virtualbox-to-vmware/
Here's an example script:
$ VBoxManage list hdds
But where do I run this command? In Windows cmd? I tried both in cmd and in Linux but I can't figure it out.