Tiger (10.4.8) hard crashes, "create default account" sequence on reboot!

Question

A couple of apps suddenly began to misbehave yesterday afternoon on a Mac OS X 10.4.8 (500 MHz DP G4) that has been rock-solid for months. I quit everything and ran a Disk Utility "Verify" check -- that crashed in the middle of the run. (Never saw that before.)
On rebooting, my Mac now jumps directly into the "Welcome to Macintosh" login sequence you see the first time a computer is booted, the screens you use to set up the default account on a fresh-out-of-the-box computer. But this one has three accounts already created, with 30 GB of data...
Fearing for the worst, I rebooted with a 10.4 install disk and ran Disk Utility from that. It correctly identified the old partition -- which seems to be full of data -- and announced that everything on the disk is OK (i.e., it "verified"). But every time I reboot the machine, I get the initial login sequence.
I need the data that was on this machine badly. Can anyone here suggest a course of action that may resurrect my old data?
Will going through the login sequence and creating a new admin account wipe out existing accounts? Is there some way to bypass the login sequence and get directly to the previously-created accounts, from which I might fiddle with something to set things right?
TH
G4 DP 500 MHz   Mac OS X (10.4.8)  

Answer 1

Thanks, Sherman, for the words of encouragement.
I've looked things over, and I think I understand the basics of what I have to do to get my data back in usable form. Let me summarize what has happened thus far and what I think I might do next:
- the result of the crash was that my old "Users/tharpold" folder was no longer recognized as a user folder; in fact, my computer recognized no users at all, requiring me to create a new user account
- I've done this, creating a user named "terryharpold", with admin privileges. That account appears to be behaving as it should, though many apps request serial numbers, etc.
Here's what I think I want to do now:
- I want to create another user, named "tharpold" (my former user name), after having renamed the old Users/tharpold folder (remember, no longer a true user directory) to Users/tharpold-old.
- I want to migrate my former "tharpold" documents and, as important, my app preferences, etc. (most of which are stored in tharpold/Library) from "tharpold-old" to the new "tharpold" user's subdirectories, thus reconstituting my former tharpold identity (Mail files, prefs, documents, etc.) in the newly-created tharpold.
- I should, I think, be able to copy the contents of my former tharpold/Documents folder to my new tharpold/Documents folder, after resetting ownership of its contents to the new tharpold account...
Here's the real question: can I copy the contents of my former tharpold/Library folder to my new tharpold/Library folder in this way? That would, if possible, retrieve my app prefs, Application Support files, Mail files, etc. But should I expect them all to copy over cleanly -- i.e., so as to be usable when I next reboot into the new tharpold account?
TH
G4 500 MHz DP   Mac OS X (10.4.8)