Sun Virtualbox - A disk image already registered error

If you receive this error (like I do after playing with Chrome OS)

A disk image with UUID {4c656719-39df-4129-ac50-3e54f5a2faa3} or file path 'D:\Downloads\chrome-os-0.4.22.8-gdgt.vmdk' is already registered.

Result Code:
E_INVALIDARG (0x80070057)
Component:
VirtualBox
Interface:
IVirtualBox {2d3b9ea7-25f5-4f07-a8e1-7dd7e0dcf667}

Solution:
Open: C:\Users\adminNUS\.VirtualBox\virtualbox.xml and delete the troublesome entry. In this case:
<Image uuid="{4c656719-39df-4129-ac50-3e54f5a2faa3}" src="D:\Downloads\chrome-os-0.4.22.8-gdgt.vmdk"/>

inside <DVDImages> tag.