STUMPED: iBook G4 powers up - Hangs at 'grey apple startup screen'

Question

ok, I'm trying to help a friend with her iBook woes. Info you need to know:
She dropped it once, while the screen was open, hard disk potentially active. Yes, it has sudden motion sensor but I'm not sure if that matters.
She brought it to me because it was performing slowly, some apps were hanging at launch and the like. I started by starting it up and taking a look around. Sure seemed slow. I updated to 10.4.11 and some Java updates. I can't recall exactly but the computer ended up hanging at some point. Might have been during the end of the installation process. I restarted and finished the update process. All that was left to update was Java and it didn't require a restart. At some point thereafter the computer gave me the spinning beach ball and was hanging. We waited a while, then restarted. On restart, it just hung on the 'grey apple startup screen'. So we waited, maybe 10 minutes and I figured something was wrong.
I force shut down the iBook. I then set another iBook (iBook 2) next to it and started it up in Firewire disk mode. I then connected the two iBooks with a firewire cable and started iBook 1 while holding down [option] and chose the disk on iBook 2 as my startup disk.
This is where it gets interesting. I assume the problem is with mismatched or badly written info on the internal disk (iBook 1), OR the disk is physically damaged. I open up Disk Utility and attempt to verify the disk (iBook 1). I get an ERROR MESSAGE: Disk failed to unmount.
Ok, try again, oh, it works this time. D.U. finds a bunch of problems. I repair the disk, I repair disk permissions.
I restart.
Computer works fine for a while. Still running slow. We open iTunes and attach an iPod. somewhere in the syncing process the system hangs, iTunes hangs, the Finder hangs. We wait, and eventually, restart.
At this point, or even sooner I would have run Apple's Hardware test utility from the iBook restore DVD. Well, my friend has misplaced it, or its at home in another state. So i'm left to my own devices.
I have run disk utility from other disks several times. It finds not a single problem.
Computer hangs at startup as previously described.
I have reset the PMU. No difference.
I would, if I had possession of the iBook DVD, run the Hardware test and, after backing up the drive, erase it and re-install the OS.
ANY IDEAS? WORKAROUNDS???
THANKS!!!!!!!

Answer 1

Another way of repairing the hard drive is booting into Safe Mode. This takes quite awhile longer than a normal startup because it does a file check and repair of the hard disk.
You will see the normal desktop. Once completely started up in Safe Mode, restart normally, and go to Applications > Utilities > Disk Utility. Click on the top hard drive icon in the left sidebar and note the S.M.A.R.T. status at the bottom right of the pane. What does it say?
Select the named boot volume in the left sidebar ("Macintosh HD" unless you've renamed it). What is the hard drive capacity and how much space remains available on it? Repair permissions on it.
Maybe this will give us a clue as to what is wrong.