Is a Blue Screen at Start-up a Hard Drive Problem?

I came back to my Powerbook after a power failure and the screen was all light blue. I restarted, getting the appropriate chime, but it only got to the point where it displayed the light blue screen again and did nothing more -- no sad face, no question mark.

I tried to…

…restart with no extensions (Shift key). Same result.

…restart after NV PRAM reset (Cmd-Opt-P-R). Start-up chime and restart, but then the same result as before.

…restart after Power Management Unit reset. Same result.

…restart into Single User Mode (Cmd-S). Same result (i.e., failed to enter SUM).

…restart into Open Firmware Mode (Cmd-Opt-O-F). Succeeded entering the Open Firmware console, but reboot afterward yielded the same result as before.

…boot from Mac OS X on an external Firewire disk. Succeeded, but internal HD did not mount.

…inspect the internal HD with Disk Utility. Disk appeared, but would not mount.

…run Repair Disk on the internal HD. Test began but failed after reporting working on catalog.

…run DiskWarrior to recreate the disk directory. The process took several hours due to reported hardware malfunctions and completed with a report of 0 directories and 0 files in the "rebuilt" directory.

I am considering removing the existing internal hard drive and replacing it with a new drive, and placing the old drive in an external HD enclosure and testing it there. My questions, then, are:

1. What else might you recommend i do to solve the problem without removing the internal drive?

2. Is it possible this could be a logic board problem? The fact that DiskWarrior detected no directories or files whatsoever, even though it saw the drive present, signals that the drive may not be communicating through the logic board at all. How might I further isolate the problem to either the board or the drive?

3. What external enclosure would you recommend for the internal drive if I remove it?

4. If it is the hard drive that has gone bad, what data recovery service(s) might you recommend?

Thanks very much for considering this problem.