System not found, even after reinstall

Question

My iBook G4 started up with a flashing question mark. When starting up from the system cd and running Disk Utility all seems fine, I can even select it as a startup disk. However, it won't start up from it. I reinstalled the system, and still nothing has changed, the flashing question mark of doom is still there. Any ideas? (also the hardware test showed no failures)
Also a way to at least be able to back up some stuff from the HD would be simply great.

Answer 1

The hard disk drive inside the computer may be accessible through use of
the FireWire Target Disk Mode procedure, where that computer is seen at
boot into FW TDM as an external hard disk drive and anything on there
found in the drive by the host (healthy) computer used to access it, could
be archived to CD or DVD media; for example.
Just because the HDD tests OK does not mean the device has a bootable
Directory anymore; it could be shot. But you do not need to access a boot-
system on that drive to make it visible as an external FW hard drive in TDM.
A good disk utility may be able to rebuild or restore (repair, maybe) the
directory of a system on the computer's hard disk drive; but it may be
marginal and the drive could actually be failing even if it passed verify
and maybe a booted Apple Hardware Test interval. Disk Warrior can
build a new directory, if the correct version is used for the OS involved.
Was the computer's drive in question, totally erased by using the booted
Installer's version of Disk Utility, and its ability to over-write a hard drive
with Zeros, so as to leave nothing readable on there, prior to reformatting
the drive for a fully new complete installation of OSX on that HDD? If that
were to be done, then the need for Disk Warrior may not be pressing. A
repair of directory damages and some other fixes is something the native
OS X Disk Utility does not do, specifically. And a new hard disk drive may
be the best repair of this situation; be sure to also test, repair, reformat a
new hard disk drive when you get a replacement one of the correct type.
If the internal drive were removed and put into an external USB2.0 case,
the contents could be read at a later time and if there are retrievable files
they could be recovered later; and a new drive in the computer could be
the fix. However, there are some fine cables and wires inside the computer
and being careful is an understatement. A slight messup and it's curtains.
And there are a pile of assorted screws and bits that have to be removed
in order to get into an iBook G4 in order to replace a hard disk drive.
There are some fairly good iFixit online guides, they appear to be free;
and that may be a way to go, in resolve the issue your iBook exhibits.
An external FireWire enclosed HD capable of booting Mac OSX is helpful
in troubleshooting a computer and also in making full computer clones;
as backup of the content and also to restore. That is preventative, but
having a clone already available from that computer could help fix it
and restore it faster, since it can be used to run utilities and test the Mac.
That idea speeds up installations since an internal computer's drive can
be wiped, zeroed, reformatted and a new clone of the machine moved
over into the computer's drive in about an hour. - An idea for the future.
If you can get the correct DiskWarrior disk utility for your computer's OS
that may be able to fix some errors on the computer's hard disk drive.
What kinds of errors did a 'repair disk' interval in the Mac's Disk Utility
tell you in the report? The booted Disk Utility should show results...
While Disk Warrior may be able to fix some issue in the hard drive,
after years of use, the drive in a portable computer (or desktop) is
likely worn to the point of unreliability.
The drive in the computer has likely reached the end of its serviceable
life span and a replacement PATA type drive of suitable specifications
is recommended as a possible path to repair the computer's issues.
Good luck & happy computing!