Boot the Powerbook from your OS 9 CD and backup your data. Then use Disk First Aid to make sure the hard drive is OK.
To try and salvage your computer, you can then boot from your OS X CD, and re-install OS X on top of everything (without erasing). Make sure to go through all the software updates again, before using the computer. If this doesn't work (or if you don't mind starting over) you can erase the hard drive, and then re-install OS X.
How did this all start? Did you install a particular beta driver?