partable USB install - have GRUB recognize installed OS

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http://crunchbanglinux.org – I seem to remember that some Live ISOs and USB installs are (or used to be) able to recognize installed operating systems on whatever PC they're used on, giving you the option to boot to the internal HD from GRUB on the Live ISO or USB.  I seem to remember there was some small code that worked with GRUB Legacy.  Is there a way to do this in GRUB 2? (HowTos)