Not possible to run stuff off xbox 360 hdd.. (Score 1)

No, it's not possible to run unsigned code or homebrew on the 360. It hasn't been, and probably won't ever be possible until we can find a way to break the keys, or the dependence on the cryptographic keys contained within the 360. Pretty much all that the mods are doing is spoofing the PFI (Physical Format Information), DMI (Disc Manufacturer Information, SS (Stealth Sectors), and video.iso (a short video) to the original information that's offset to a different spot on the disc. In layman's terms, it pretends that you're running a storebought xbox360dvd with all of its original disc information (ie: disc stamped in kanagawa, japan) while in fact you are running a verbatim dvd9.