OSX Bootable from External HDD?

Couple of things. If I wanna reinstall Leopard on a computer, but want to do so from an external harddrive, what would be the best solution? (I have the install discs). Do I need to create a .iso of the 2 discs and throw those on the external hdd (would it be bootable, say if the hdd of the computer i wanted to fix was messed up) or is there another way of creating a bootable OS on the external.

Thanks, I really appreciate it.

Press Option-Command-Shift-Delete
during startup this boots mac os x from an alternative volume e.g. external hard disk

Z_KNILL

using external hd for leopard with pbk (ppc g4) as main startup

hi,

i personally do not like leopard all that much (lots of reasons) and, after installing it on my macbook, have not installed it on my powerbook ppc g4 (10.4.11, 1.2 GHz, 1.25 GB DDR SDRAM). but, there are a few apps i like that run ONLY on leopard. if i install leopard on an external hd and choose it as the startup disc and reboot, will i be able to use laptop as before and will i be able to run those leopard-only apps? will i experience any problems with laptop pre-leopard apps (i can't imagine why since pre-leopard apps run fine on leopard installed macbook)? should i put leopard apps on laptop or leopard hd?

sorry for such a simple question(s) but i've never really done this before. (i am thinking of an OWC pocket type drive of 40 GB) according to leopard specs (http://www.apple.com/macosx/techspecs/) i should be able to do this.

thanks for any help

rich ratzan