[G4] help with 10.4

[Mark Swanson]

My TiBook is and has been working fine but my Quicksilver (two drives) 
is giving me a problem.  The original 80 gig drive is running 10.3.9 
and I carbon copied it to an external firewire drive.  My second drive 
is a 200 gig internal running 10.4.3.  My plan was to back up my 80 gig 
to the external,  then reformat and install 10.4.  But, in the middle 
of this, my 200 gig  went schizo and won't let me log in.  I am leery 
of erasing my main 80 gig if the 200 gig drive (and 10.4.3) is going 
wacky.  The larger drive won't recognize my user password or my 
administrator password.  Should I toss to system folders on the 200 and 
re-intall?  I fixed permission on every drive before I started, ran 
Disk utility on every drive, and then ran Disk warrior on every drive.  
Why won't the 200 let me in?  Is there a work around besides 
reformatting and re-installing?  My big concern is a very large iTunes 
music folder on the 200 gig drive that is too big to put anywhere else, 
at the moment.  Any suggestion would be greatly appreciated