Same Old Hard Drive Failure... with a twist

Question

After the odd failure of my formerly reliable and beloved 17" Powerbook G4 I did some investigation.
(capitalized words are just to help make the key words stick out)
I did the standard list of trouble shooting with the system DVDs. REPAIR PERMISSIONS: Successful. REPAIR DISK: Failed. INVALID NODE STRUCTURES were found and after it tried to REBUILD CATALOG B-TREE there was and ERROR: THE UNDERLYING TASK REPORTED FAILURE ON EXIT.
So i ran the EXTENDED HARDWARE TEST.
I got an error in the mass storage: 2STF/8/3:ATA-100 ata-6-master
After several attempts to turn my computer on the furthest I could get was the login screen. Once I typed in my password, the computer would load for a long time then bring me to a DARWIN login screen. I don't know Unix commands so I didn't know what to do. Eventually I got back to the more friendly Aqua Login. This kind of thing happened many times with no sucessful login to my desktop (although Darwin login worked but I don't know how to use it.)
I looked on several online discussions and found that I was not entirely alone with this error. Everyone seems to have similar symptoms and a similar troubleshooting method, etc.
That said, here are the two reasons why I thought my case was worthy to post:
1. Every discussion about this error I have read so far has had the same symptoms (erratic behavior, super slow running simple tasks, unexplained crashing of simple applications, slow boot and login times, etc) the only difference is, their symptoms crept in slowly over a couple months. In my case I was using the computer on and off for about 5 hours. The first 3 or 4 hours of using it were absolutely unremarkable. The system worked just as fine as it always did. Then, in the last hour, after no major changes from the other 4 hours (no downloads, installations, moving, power adapter was in the whole time with no storms, etc.), the strange symptoms began to occur. I checked the processes and everything seemed to be running fine according to the ACTIVITY MONITOR but the system was clearly bogged down somehow. I decided to do the usual fix and simply RESTART. After that I was never able to login and currently if I turn the power on, the gray screen with the apple comes up and the loading circle (not the rainbow of death one, but the line one) appears but it just spins for a while then shuts off. IN SHORT: the difference is my computer's symptoms appeared and took over in a matter of an hour or two rather than months like many other peoples'
2. I am a silly boy and I've never done any real back up. If my hard drive has truly bitten the dust, what is the likelihood that I've lost everything?
Excuse my wordiness, brevity was never my talent.
〜さむさむ (samusamu)
17" Powerbook G4   Mac OS X (10.4.6)  

Answer 1

You have two problems.
One is that your file directories are seriously damaged. This is clear from the notations in Disk Utility.
The other is that your HD is about to fail. This is clear from the AHT error code: 2STF/8/3:ATA-100 ata-6-master.
If it wasn't for the message in AHT, I might suggest that you try running DiskWarrior on your internal drive to see if it can fix the damaged directories. It may not hurt to try that anyway.
Either way, I would suggest that if you have access to another FireWire equipped Mac, you boot your PB into target disk mode and attempt to retrieve your personal data (docs, pictures, music, etc.) as soon as possible.
If you are unable to boot the machine into target disk mode, you might want to try using Data Rescue II from Prosoft. This app is quite good, but it will need to be installed on another machine or bootable volume on an external drive.
Should Data Rescue not work, you'll have to go to a third-party to help you with data recovery.
Last, if you don't have a warranty or an APP, it's time to start shopping for a new HD.
Good luck.