PowerBook G4...gone

I just tried to restart my PowerBook G4 and...it won't turn back on. I installed some security update...would that have anything to do with it? It turns on, plays the chime, and the apple logo shows up and the hard drive spins and then the little scroll thing comes on the screen and the hard drive turns off and the screen goes black. What can I do? Is Applecare the only option?

I booted from the installer disk and ran disk repair and it came up with this :

Verify and Repair disk "Macintosh HD"
Checking HFS Plus volume
Checking Extents Overflow file
Checking Catalog file
Overlapped extent allocation (file 946191d)
Overlapped extent allocation (file 946191d)
Overlapped extent allocation (file 3277182d)
Checking multi-linked files
Checking Catalog hierarchy
Checking volume bitmap
Checking volume information
*Invalid volume free block count*
(It should be 2515789 instead of 2515802(
*Volume header needs minor repair*
~Repairing volume~
*The volume Macintosh HD could not be repaired*

**Error: The underlying task reported failure on exit**


1 HFS volume checked
**1 volume could not be repaired because of an error**
Repair attempted on 1 volume
**1 volume could not be repaired**

(I typed the entire thing on my sidekick)

what do I do now?

Oh thank you all so much! I was able to get all of the stuff I wanted/needed off my hard drive (although I now realized that all of my non-music iTunes purchases are gone) and am reinstalling OS x now. Thanks!!