I am seriously considering buying a Mac Pro .... If at all possible, I would like to be able to dual boot, with Leopard or Tiger. Is it possible to boot a Mac Pro with Tiger, from an internal HD or external FW HD? If there is no way possible to boot a Mac Pro from Tiger, is there an emulator that will allow me to run most (or all?) of my old apps that I’ve been running on my iBook G4 1Ghz (running Tiger)? Thanks.

Most of the MacPro machines shipped before those announced in January '08 shipped with a version of 10.4 (exact version varies depending upon production date). I'm not sure if the post January '08 machines can boot from Tiger. Usually you cannot backup to an OS version that pre-dates when the hardware was manufactured. The Mactracker application says that these machines shipped with at least 10.5.1

What programs were you interested in running? Unless they are OS 9 programs they may work quite well under Leopard.

There is a lot of info on old programs and Leopard. If you go to Mac forums
there is a thread on getting Tiger to run on the new Mac Pro 2.8. Pay very close attention to useing the migration assistant on moving old programs.
It is better to do a clean install on old programs and use the assistant for
data.

lechtmmg