repair v.7 installation

[PJ]

I believe that my installation should be salvageable but I do not know 
how to phrase my search question.
Here is the problem:
Apparently due to some connector problem in the computer one or some 
files were damaged. I ran a regenerating program on the disk and all 
sectors are readable.
How can I locate the problem files and repair or reinstall them without 
damaging other files?
 From trying to boot the system, it appears that the problem is related 
to the login files: I boot to safe mode and get the logon prompt which 
is not accepted. I then get to the single user mode and can read the 
contents of the root (top or main) directory and subdirectories.
The command "df" returns "-70016" under Avail and "104%" under Capacity, 
Mounted on / .

Or is it possible to reinstall the system from the installation CD? I 
would like to avoid having to reinstall all the programs that run on 
this local development server - Apache, Samba, Cups, php, pstgresql, etc.

Thanks for any help and/or suggestions.
Phil Jourdan