Leopard and USB As Startup Volume
In a word… “Don’t.” It’s not that it can’t or shouldn’t… it’s kind of a boondoggle for most.
Use your time to best advantage and begin with restoring to dual layer DVD or IEEE 1394 (FireWire). That’s your best bet.
That said, There have been enough people asking in my other topic “Installing Leopard from DMG” why it won’t work with their USB drive. I don’t know the full technical answer to satisfy those who are truly asking for a technical explanation… I just know Apple has been fairly consistent with prohibiting the booting of Tiger and now Leopard on USB. I vaguely recall Panther launching on a USB mounted drive (could be mistaking that for something else though).
PS – I don’t know how you came by your image of Leopard. I don’t want or need to know how you came by your image of Leopard. I trust yours’ came by the one of two ways Apple has made it available: WWDC or ADC.