The first machine I tried to install my shiny new copy of Tiger onto was my Powerbook G3 Lombard (Bronze Keyboard). That's when I found out that Apple decided to remove my laptop from the list of supported installs.
Now I had only three options: (1) stay with OSX 10.3.9, (2) wait for XPostFacto to support Tiger, or (3) find a workaround. I chose door number three..
I had just spent a large chunk of money on new memory and a larger hard drive only to find out that Apple's newest OS won't work. Some internet searching proved that the pre-releases of Tiger did work with the Lombard Powerbooks, so my belief was that Apple just changed the installer to exclude my favorite computer. I was correct. Here is how I was able to install OSX 10.4 on my Powerbook G3 Lombard.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050430144551596