element@element-laptop:~$ VBoxManage sharedfolder add "Windows XP" -name "Shared Stuff" "/VBShare"
VirtualBox Command Line Management Interface Version 1.5.6
(C) 2005-2008 innotek GmbH
All rights reserved.

Usage:

VBoxManage sharedfolder     add <vmname>|<uuid>
                            -name <name> -hostpath <hostpath>
                            [-transient] [-readonly]


Syntax error: Invalid parameter '/VBShare'