Here’s a great tip at macosxhints.com that makes installing Leopard much, much quicker and easier; in a nutshell, you create a disk image of the DVD with Disk Utility, then run a special .mpkg file from the image: Install OS X to a different volume without rebooting.

When you do this, you don’t need to restart the Mac to install Leopard, and it runs at the speed of a RAM disk.

I’m creating an external Firewire boot disk for the indispensable Disk Warrior hard drive repair tool (so I can fix the internal startup disk if anything goes wrong, which it will, according to Murphy), and this little trick saved a lot of time.