This video tutorial from bobby93macboy shows how to install Mac OS Leopard operating system and make it bootable.
Hard drive partition - it's a logical sector of your whole hard disc which can be used as a separate hard disc.
To make partitions, open Disc Utility using Spotlight search.
Select hard disc you want to partition and click Partition tab.
This tab allows you to adjust size for each partition your external or inner hard disc contains.
Enter partition size, name your new partition, make sure it uses Mac OS extended journaled format. You can divide your disc into maximum 16 partitions.
Then click Apply.
Beware that formatting and dividing into partitions will erase all information on your hard disc.
Bootable OS installation on an external hard drive helps when computer's hard drive fails. To make Mac OS bootable disc, insert Mac OS Leopard installation DVD.
From installer welcome window click Install Mac OS X.
Click Continue, agree to licence agreement, then click Mac OS Boot disc option.