Boot problem

I was working on a client's home PC running Windows XP
Pro. I moved the swap file from the very small C: to the
much larger new F: that I installed. Immedeatly the PC
rebooted and stopped with an error message that states:
Windows could not start because a file is missing or
corrupt - Windows\System32\Config\System. I was running
relatively fine before that. I was shocked because I had
moved swap files before and not had any problem. I could
not even boot into safe mode or use the Last Known Good
Configuration with success. Even the Recovery option did
nothing. All that did was bring me to a DOS prompt and I
looked in the Windows\System32\Config directory and saw a
System file but with no extension to any files. In DOS I
loaded from a boot disk, it showed a Systen.sav file. I
ran Scandisk and it showed some corrupt files in that
area and I chose to fix them, but it did not help any.

If I run XP setup over the first XP, will it repair it
and retain the original settings, or do a fresh install??
Or should I install a second XP and copy the files from
that Config folder to the first XP and would that fix the
first XP and retain the settings??

This seems unusual that this happened and the client
later stated that she had been having virus problems and
had no antivirus software. Could a virus be the culprit??

Thanks for any and all replies.