1. klick on windows icon and write 'cmd' and press ENTER to open a terminal in windows.
2. change to VirtualBox directory
cd C:\Program Files\Sun\VirtualBox
3. run VBoxManage.exe
C:\Program Files\Sun\VirtualBox>VBoxManage.exe clonehd "D:\vm\WinXP.vdi" "D:\vm\WinXp-clone.vdi"
Sun VirtualBox Command Line Management Interface Version 3.1.8
(C) 2005-2010 Sun Microsystems, Inc.
All rights reserved.
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%
Clone hard disk created in format 'VDI'. UUID: 609c2e84-981c-4e73-b32b-dd7fbc5ee
4c7