Corrupted passwd file?

["David R. Kohel" <kohel@math.nus.edu.sg>]

I think I have a dying hard disk; the only other option is 
some virus.

I was upgrading libc & gcc compliers (from potato) on my laptop 
over a PLIP connection when I gradually started losing priviledges 
to ftp and telnet into the machine.  Once I logged out I couldn't 
log back in, even as root.  At the login prompt I get something 
like "Incorrect password for 'UNKNOWN' on tty1."  I can't even 
reboot, since ctrl-alt-del just retorts maliciously: 
"You don't exist. Go away."

So far I haven't even been able to get rescue/root floppies 
to work: ("Unable to open console.") but that may just be due 
to the corrupt disks I'm trying to salvage.  

I get no other symptoms of a dying disk: the boot sequence seems
to go smoothly with no apparent corruption of the filesystem.

????

--David