The guide posted here http://sneekygeekers.com/2012/12/08/how-to-install-a-virtualbox-guest/ described how to install Xubunu 12.10 in virtualbox , for those that would like to start it from the menu , instead of opening virtuabox settings then starting the virtual machine here is how to do it.
First open the virtualbox settings program click on your virtual machine and goto the machine settings , create shortcut on desktop. Once has been created, move it to ~/.local/share/applications. Alternatively create the .desktop file by hand , it should look something like this
Comment=Starts the VirtualBox machine Xubuntu 12.10
Exec=/usr/lib/virtualbox/VirtualBox –comment “Xubuntu 12.10” –startvm “47cdc8bb-dadb-4d30-814d-cb63870f1a3c”
Personally I use a different icon for my launcher. I have some here in my dropbox account that I will share for a short time. once downloaded extracted the icons and place them in ~/.local/share/icons likewise if you have any of your own icons you wish to use.