====== Free up space in the vbox image ======

Copy all the space to a new file
  dd if=/dev/zero of=/tmp/empty.dd bs=1048576

delete the empty file
  rm /tmp/empty.dd

Shutdown the server and run the following command in DOS to get in the right working folder

  cd "C:\Program Files\Oracle\VirtualBox"

Then run this command to rebuild the disk image

  VBoxManage modifymedium --compact c:\xxxx.vdi